KVM: arm/arm64: Get rid of kvm_timer_flush_hwstate

Now when both the vtimer and the ptimer when using both the in-kernel
vgic emulation and a userspace IRQ chip are driven by the timer signals
and at the vcpu load/put boundaries, instead of recomputing the timer
state at every entry/exit to/from the guest, we can get entirely rid of
the flush hwstate function.

Signed-off-by: Christoffer Dall <cdall@linaro.org>
Acked-by: Marc Zyngier <marc.zyngier@arm.com>