arm64: KVM: Switch vgic save/restore to alternative_insn

So far, we configured the world-switch by having a small array
of pointers to the save and restore functions, depending on the
GIC used on the platform.

Loading these values each time is a bit silly (they never change),
and it makes sense to rely on the instruction patching instead.

This leads to a nice cleanup of the code.

Acked-by: Will Deacon <will.deacon@arm.com>
Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
(cherry picked from commit 8a14849b4a355278f0b7baf6e2da7dc7144a23e8)
Signed-off-by: Alex Shi <alex.shi@linaro.org>

Conflicts:
	arch/arm64/include/asm/kvm_asm.h
5 files changed