KVM: arm64: vgic-v3: Add ICV_IAR1_EL1 handler

KVM: arm64: vgic-v3: Add ICV_IAR1_EL1 handler

BugLink: https://bugs.launchpad.net/bugs/1673564
Add a handler for reading the guest's view of the ICC_IAR1_EL1
register. This involves finding the highest priority Group-1
interrupt, checking against both PMR and the active group
priority, activating the interrupt and setting the group
priority as active.

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>
Reviewed-by: Christoffer Dall <cdall@linaro.org>
Signed-off-by: Christoffer Dall <cdall@linaro.org>
(backported from commit 132a324ab62fe4fb8d6dcc2ab4eddb0e93b69afe)
[ dannf: Dropped SYS_ prefix on ICV_IAR1_EL1 macro, which wasn't
  added upstream until 0e9884fe ]
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>