Fix two compiler warnings in memory.c

[rgommers]

First warning:

[4339/5327] Building C object driver/others/CMakeFiles/driver_others.dir/memory.c.o
.../OpenBLAS/driver/others/memory.c: In function 'blas_shutdown':
.../OpenBLAS/driver/others/memory.c:3257:10: warning: passing argument 1 of 'free' discards 'volatile' qualifier from pointer target type [-Wdiscarded-qualifiers]
 3257 |     free(newmemory);
      |          ^~~~~~~~~
In file included from .../OpenBLAS/common.h:83,
                 from .../OpenBLAS/driver/others/memory.c:74:
.../.pixi/envs/default/x86_64-conda-linux-gnu/sysroot/usr/include/stdlib.h:482:25: note: expected 'void *' but argument is of type 'volatile struct newmemstruct *'
  482 | extern void free (void *__ptr) __THROW;
      |                   ~~~~~~^~~~~

The use of volatile for newmemstruct seems on purpose, and there are more such constructs in this file. The warning appeared after gh-4451 and is correct. The free prototype doesn't expect a volatile pointer, hence this change adds a cast to silence the warning.

Second warning:

...OpenBLAS/driver/others/memory.c:2565:14: warning: 'alloc_hugetlb' defined but not used [-Wunused-function]
 2565 | static void *alloc_hugetlb(void *address){

The added define is the same as is already present in the TLS part of memory.c. This follows up on gh-4681.

[martin-frbg]

Thanks, had seen those and planned to address them together with some Windows Clang noise.