configs/rock5b: Switch to mainline TrustedFirmware

The Rock 5b board support currently uses a binary trusted firmware
blob from the rockchip-rkbin package. Recently, the Rock 5b's SoC,
i.e., the rk3588, received mainline TrustedFirmware-A support:

https://review.trustedfirmware.org/c/TF-A/trusted-firmware-a/+/21840
https://review.trustedfirmware.org/c/TF-A/trusted-firmware-a/+/29363

This support was recently released as part of the v2.12 version of
the TrustedFirmware-A. This patch changes the defconfig from using
the rockchip-rkbin atf binary blob to building the TrustedFirmware-A
v2.12 for the rk3588 from source.

Signed-off-by: Kilian Zinnecker <kilian.zinnecker@mail.de>
Signed-off-by: Julien Olivain <ju.o@free.fr>

configs/rock5b_defconfig

@@ -23,9 +23,15 @@ BR2_LINUX_KERNEL_NEEDS_HOST_OPENSSL=y
 BR2_LINUX_KERNEL_NEEDS_HOST_PYTHON3=y
 BR2_PACKAGE_LINUX_FIRMWARE=y
 BR2_PACKAGE_LINUX_FIRMWARE_RTL_8169=y
+BR2_TARGET_UBOOT_NEEDS_ATF_BL31=y
+BR2_TARGET_UBOOT_NEEDS_ATF_BL31_ELF=y
 BR2_PACKAGE_ROCKCHIP_RKBIN=y
 BR2_PACKAGE_ROCKCHIP_RKBIN_TPL_FILENAME="bin/rk35/rk3588_ddr_lp4_2112MHz_lp5_2736MHz_v1.12.bin"
-BR2_PACKAGE_ROCKCHIP_RKBIN_BL31_FILENAME="bin/rk35/rk3588_bl31_v1.40.elf"
+BR2_TARGET_ARM_TRUSTED_FIRMWARE=y
+BR2_TARGET_ARM_TRUSTED_FIRMWARE_CUSTOM_VERSION=y
+BR2_TARGET_ARM_TRUSTED_FIRMWARE_CUSTOM_VERSION_VALUE="v2.12"
+BR2_TARGET_ARM_TRUSTED_FIRMWARE_PLATFORM="rk3588"
+BR2_TARGET_ARM_TRUSTED_FIRMWARE_IMAGES="bl31/bl31.elf"
 BR2_TARGET_ROOTFS_EXT2=y
 BR2_TARGET_ROOTFS_EXT2_4=y
 BR2_TARGET_ROOTFS_EXT2_SIZE="250M"