KVM: ARM: vgic: abstract MISR decoding

Instead of directly dealing with the GICH_MISR bits, move the code to
its own function and use a couple of public flags to represent the
actual state.

Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

diff --cc include/kvm/arm_vgic.h
Simple merge

diff --cc virt/kvm/arm/vgic.c
Simple merge