Improve mixing usage fileio and fileXio

[fjtrujy]

Description

The main scope of this PR is to avoid having unused functions within the embedded ELF, unfortunately, the linker and compiler aren't that clever and require some help to make it work better.
More concretely most of the unused functions belong to the library used for performing IO operations, either fileio or fileXio. Having both in the binary first makes the a waste of space, and secondly could deal with problems if you start mixing by mistake fd from/to fileio/filexio.

How I did it:

• rom0_info contains some information about the ROM0 included in the console, it was always using fileio for accessing the ROM0 content, now, I have created a possibility to inject via driver the functions used to deal with IO operations.
• osd_config used functions from rom0_info, so the same strategy was created here.
• There was something wrong additionally in osd_config, it was using some _libcglue_timezone_update functions, and it shouldn't, because libkernel.a shouldn't have any kind of dependency, for still allowing a way of using it without newlib. In order to facilitate the usage of these logic to the final user, I have created 2 new functions in ps2sdkapi.h file, ps2sdk_setTimezone and ps2sdk_setDaylightSaving which automatically will use the proper IO library and the expected callback to _libcglue_timezone_update.
• _libcglue_timezone_update used those osd_config functions, so now it injects the driver with the proper IO functions. Additionally, the logic for setting the timezone was updated having as reference how PSP did.
• The way of setting the _ps2sdk_XXX functions, now have changed. Previously we set by default fileIO functions, and then later on, it was replaced with fileXio functions. Now, however, they have NULL value as default, and then weak functions called __set_ps2sdk_XXX pointing to fileIO have been created; then strong functions pointing to fileXio have been created, in the way that as soon as the user link the binary with fileXio automatically all the fileio functions will be removed from the binary. All these functions must be called before the _ps2sd_XXX is used. This also require to do an extra trick to make it work, https://stackoverflow.com/a/22178564
• fileXio EE library has been improved, it now has a specific compilation per function, and it helps to link and strip unused symbols. Other not needed functions were removed.
• A specific sample to check the timezone has been created.
• A specific sample to check fileXio usage has been created.
• Other minor clean/up changes.

Results:

• I have used my filesystem sample from ps2_drivers https://github.com/fjtrujy/ps2_drivers/tree/main/samples/filesystem_sample

-rwxr-xr-x  1 fjtrujy  staff  535656 Dec  6 22:06 filesystem_sample.elf
-rw-r--r--@ 1 fjtrujy  staff  549524 Dec  6 21:05 filesystem_sample_old.elf
-rw-r--r--  1 fjtrujy  staff  165720 Dec  6 22:09 filesystem_sample_old_packed.elf
-rwxr-xr-x  1 fjtrujy  staff  462900 Dec  6 22:08 filesystem_sample_old_strip.elf
-rw-r--r--  1 fjtrujy  staff  163144 Dec  6 22:10 filesystem_sample_packed.elf
-rwxr-xr-x  1 fjtrujy  staff  451508 Dec  6 22:08 filesystem_sample_strip.elf

It reduces 15KB when the binary contains debug symbols, 11KB when the binary is stripped, and 2.6KB when the binary is packed.

• Let's check now OPL (I have also added EE_CFLAGS += -fdata-sections -ffunction-sections -flto and EE_LDFLAGS += -fdata-sections -ffunction-sections -flto -Wl,--gc-sections) flags:

WIP: I will try to test it tomorrow :(

Finally, I would like some of you to test those improvements, to fully assure that everything is working as expected. Especially OPL which is the most critical piece of software we actually support.

[uyjulian]

These set of changes are in a good direction.

LGTM

[fjtrujy]

I think this header shouldn't be here, but I would like to hear your opinions... @rickgaiser and @uyjulian

[uyjulian]

Maybe ps2sdk-libcglue.h?

[fjtrujy]

This is crucial to save RAM, what do you think should be a good number here?
I would say that 64 is fair enough....