boot/ti-k3-r5-loader: use BR2_PACKAGE_HOST_ARM_GNU_TOOLCHAIN_SUPPORTS

ti-k3-r5-loader can only be built on x86_64 or aarch64 hosts due
to ARM gnu toolchain dependency.

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

boot/ti-k3-r5-loader/Config.in

@@ -1,6 +1,7 @@
 config BR2_TARGET_TI_K3_R5_LOADER
 	bool "ti-k3-r5-loader"
 	depends on BR2_aarch64
+	depends on BR2_PACKAGE_HOST_ARM_GNU_TOOLCHAIN_SUPPORTS
 	select BR2_TARGET_TI_K3_BOOT_FIRMWARE # binman
 	help
 	  Separate U-Boot SPL build for R5 core on TI's K3 processors.