xen: remove redundant external patches

Xen is now build from the latest Xen release, RELEASE-4.18.0 so all the
external Xen patches can now be removed.

Xen commit d4fb5f166c2b ("optee: enable OPTEE_SMC_SEC_CAP_MEMREF_NULL
capability") was introduced in RELEASE-4.16.0 so remove the patch
0001-optee-enable-OPTEE_SMC_SEC_CAP_MEMREF_NULL-capabilit.patch.

Xen commit 5d2d5365ffad ("optee: immediately free RPC buffers that are
released by OP-TEE") was introduced in RELEASE-4.17.0 so remove the patch
0001-optee-immediately-free-RPC-buffers.patch.

Xen commit b75838ad6c4f ("xen/arm: optee: Allocate anonymous domheap
pages") was introduced in RELEASE-4.16.0 and addresses the problem that the
patch 0001-Revert-xen-arm-Restrict-the-amount-of-memory-that-do.patch tries
to solve, so remove the patch.

Xen is now configured by merging additional external configuration with the
defconfig so remove the now redundant patch
0001-Set-config-for-OP-TEE.patch.

Xen commit 1c3ed9c90873 ("xen/arm: optee: Fix arm_smccc_smc's a0 for
OPTEE_SMC_DISABLE_SHM_CACHE") was introduced in RELEASE-4.16.0 so remote
the patch 0001-xen-arm-optee-Fix-arm_smccc_smc-s-a0-for-OPTEE_SMC_D.patch.

Signed-off-by: Jens Wiklander <[email protected]>
Reviewed-by: Jerome Forissier <[email protected]>

common.mk

@@ -269,9 +269,6 @@ endif
 
 ifeq ($(XEN_BOOT),y)
 DEFCONFIG_XEN=--br-defconfig build/br-ext/configs/xen.conf
-# The version of Xen provided by Buildroot needs a few patches to work with
-# OP-TEE
-BR2_GLOBAL_PATCH_DIR=../build/br-ext/patches
 endif
 
 BR2_PER_PACKAGE_DIRECTORIES ?= y