arm64: KVM: Implement timer save/restore

Implement the timer save restore as a direct translation of
the assembly code version.

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
(cherry picked from commit 1431af367e52b08038e78d346822966d968f1694)
Signed-off-by: Alex Shi <alex.shi@linaro.org>

Conflicts:
	arch/arm64/kvm/hyp/Makefile
	arch/arm64/kvm/hyp/hyp.h
4 files changed