ARM: Make CONFIG_CPU_V7 valid for 32bit ARMv8 implementations

ARM: Make CONFIG_CPU_V7 valid for 32bit ARMv8 implementations

ARMv8 is a superset of ARMv7, and all the ARMv8 features are
discoverable with a set of ID registers. It means that we can
use CPU_V7 to guard ARMv8 features at compile time.

This commit simply amends the CPU_V7 configuration symbol comment
to reflect that CPU_V7 also covers ARMv8.

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Zaid Al-Bassam <zalbassam@google.com>
Tested-by: Florian Fainelli <f.fainelli@gmail.com>
Link: https://lore.kernel.org/r/20230317195027.3746949-7-zalbassam@google.com
Signed-off-by: Will Deacon <will@kernel.org>