arm64: KVM: Make PSCI_VERSION a fast path

For those CPUs that require PSCI to perform a BP invalidation,
going all the way to the PSCI code for not much is a waste of
precious cycles. Let's terminate that call as early as possible.

Change-Id: Ia5110c05b0173e5be20c8d5e43f06fc2e546a58f
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Patch-mainline: linux-arm-kernel @ 01/08/18, 9:32
Signed-off-by: Channagoud Kadabi <ckadabi@codeaurora.org>