arch/Config.in.arm: add BR2_ARM_CPU_ARMV8

In order to prepare the addition of ARM64 cores, add the blind
BR2_ARM_CPU_ARMV8 option.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

arch/Config.in.arm

@@ -55,6 +55,9 @@ config BR2_ARM_CPU_ARMV7A
 config BR2_ARM_CPU_ARMV7M
 	bool
 
+config BR2_ARM_CPU_ARMV8
+	bool
+
 choice
 	prompt "Target Architecture Variant"
 	default BR2_arm926t