boot/arm-trusted-firmware: use BR2_PACKAGE_HOST_ARM_GNU_TOOLCHAIN_SUPPORTS

Allow to enable BR2_TARGET_ARM_TRUSTED_FIRMWARE_NEEDS_ARM32_TOOLCHAIN
option on aarch64 hosts using HOST_ARM_GNU_TOOLCHAIN_SUPPORTS, in order
to build an ATF firmwares that require a pre-built bare metal toolchain
(rockpro64_defconfig).

[Romain: improve commit log]
Signed-off-by: Bryce Johnson <bryce@redpinelabs.com>
Signed-off-by: Romain Naour <romain.naour@smile.fr>

boot/arm-trusted-firmware/Config.in

@@ -249,7 +249,7 @@ config BR2_TARGET_ARM_TRUSTED_FIRMWARE_NEEDS_DTC
 config BR2_TARGET_ARM_TRUSTED_FIRMWARE_NEEDS_ARM32_TOOLCHAIN
 	bool "Needs arm-none-eabi toolchain"
 	depends on BR2_aarch64
-	depends on BR2_HOSTARCH = "x86_64"
+	depends on BR2_PACKAGE_HOST_ARM_GNU_TOOLCHAIN_SUPPORTS
 	help
 	  Select this option if your ATF board configuration requires
 	  an ARM32 bare metal toolchain to be available.