arm64: KVM: Support X-Gene guest VCPU on APM X-Gene host

This patch allows us to have X-Gene guest VCPU when using KVM arm64
on APM X-Gene host.

We add KVM_ARM_TARGET_XGENE_POTENZA for X-Gene Potenza compatible
guest VCPU and we return KVM_ARM_TARGET_XGENE_POTENZA in kvm_target_cpu()
when running on X-Gene host with Potenza core.

[maz: sanitized the commit log]

Signed-off-by: Anup Patel <anup.patel@linaro.org>
Signed-off-by: Pranavkumar Sawargaonkar <pranavkumar@linaro.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

diff --cc arch/arm64/include/uapi/asm/kvm.h
Simple merge

diff --cc arch/arm64/kvm/guest.c
Simple merge

diff --cc arch/arm64/kvm/sys_regs_generic_v8.c
Simple merge