KVM: arm64: vgic-v3: Add ICV_HPPIR1_EL1 handler

KVM: arm64: vgic-v3: Add ICV_HPPIR1_EL1 handler

BugLink: https://bugs.launchpad.net/bugs/1673564
Add a handler for reading the guest's view of the ICV_HPPIR1_EL1
register. This is a simple parsing of the available LRs, extracting the
highest available interrupt.

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 2724c11a1df4b22ee966c04809ea0e808f66b04e)
[ dannf: Drop the SYS_ prefix and move the ICV_HPPIR1_EL1 macro definition
  from asm/sysreg.h to asm/arch_gicv3.h for consistency with code
  prior to 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>