support/testing: test_edk2: bump ATF version to 2.9 for binutils 2.39+ support

Following the toolchain-external-arm-aarch64 bump to version 12.2-rel1
by commit [1], binutils 2.39 is now provided by the toolchain.

This new binutils version break the ATF build due to new linker warnings as
reported by the EDK2 test:

  ld.bfd: warning: bl2.elf has a LOAD segment with RWX permissions

From [2]
"Users of GNU ld (BPF) from binutils 2.39+ will observe multiple instaces
 of a new warning when linking the bl*.elf in the form:

   ld.bfd: warning: stm32mp1_helper.o: missing .note.GNU-stack section implies executable stack
   ld.bfd: NOTE: This behaviour is deprecated and will be removed in a future version of the linker
   ld.bfd: warning: bl2.elf has a LOAD segment with RWX permissions
   ld.bfd: warning: bl32.elf has a LOAD segment with RWX permissions

 These new warnings are enbaled by default to secure elf binaries:
  - https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=ba951afb99912da01a6e8434126b8fac7aa75107
  - https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=0d38576a34ec64a1b4500c9277a8e9d0f07e6774
"

Bump the ATF custom version to 2.9 for binutils 2.39+ support.

[1] 90404e84c1c9d65b4f38cc3ebc30ef6a4da314cb
[2] https://github.com/ARM-software/arm-trusted-firmware/commit/1f49db5f25cdd4e43825c9bcc0575070b80f628c

Fixes:
https://gitlab.com/buildroot.org/buildroot/-/jobs/4581325484

Signed-off-by: Romain Naour <romain.naour@smile.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

support/testing/tests/boot/test_edk2.py

@@ -24,6 +24,8 @@ class TestEdk2(infra.basetest.BRTest):
         BR2_TARGET_GRUB2=y
         BR2_TARGET_GRUB2_ARM64_EFI=y
         BR2_TARGET_ARM_TRUSTED_FIRMWARE=y
+        BR2_TARGET_ARM_TRUSTED_FIRMWARE_CUSTOM_VERSION=y
+        BR2_TARGET_ARM_TRUSTED_FIRMWARE_CUSTOM_VERSION_VALUE="v2.9"
         BR2_TARGET_ARM_TRUSTED_FIRMWARE_PLATFORM="qemu_sbsa"
         BR2_TARGET_ARM_TRUSTED_FIRMWARE_FIP=y
         BR2_PACKAGE_HOST_GENIMAGE=y