arm64/armv8: Set ARCH_ARMV8_EXTENSION depend on ARCH_ARM64

This will remove "ARCH_ARMV8_EXTENSION=0" from ".config" when unneeded.

Change-Id: Idd4ad67fb4a3efdb0864803f87c6b5f508fb4364
Signed-off-by: Elyes HAOUAS <ehaouas@noos.fr>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/49598
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Julius Werner <jwerner@chromium.org>
diff --git a/src/arch/arm64/armv8/Kconfig b/src/arch/arm64/armv8/Kconfig
index f70b529..c767b06 100644
--- a/src/arch/arm64/armv8/Kconfig
+++ b/src/arch/arm64/armv8/Kconfig
@@ -14,6 +14,8 @@
 	bool
 	select ARCH_RAMSTAGE_ARM64
 
+if ARCH_ARM64
+
 config ARCH_ARMV8_EXTENSION
 	int
 	default 0
@@ -25,3 +27,5 @@
 	  All ARMv8 implementations are downwards-compatible, so this does not
 	  need to be changed unless specific features (e.g. new instructions)
 	  are used by the SoC's coreboot code.
+
+endif # ARCH_ARM64