KVM: arm/arm64: vgic-v3: Add accessors for the ICH_APxRn_EL2 registers

KVM: arm/arm64: vgic-v3: Add accessors for the ICH_APxRn_EL2 registers

BugLink: https://bugs.launchpad.net/bugs/1673564
As we're about to access the Active Priority registers a lot more,
let's define accessors that take the register number as a parameter.

Tested-by: Alexander Graf <agraf@suse.de>
Acked-by: David Daney <david.daney@cavium.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <cdall@linaro.org>
(backported from commit 63000dd8006dc987db31ba670edc23142ea91e01)
[ dannf: trivial context fix ]
Signed-off-by: dann frazier <dann.frazier@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Acked-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>