KVM: arm64: vgic-v3: Add ICV_IAR1_EL1 handler

KVM: arm64: vgic-v3: Add ICV_IAR1_EL1 handler

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 <[email protected]>
Acked-by: David Daney <[email protected]>
Reviewed-by: Eric Auger <[email protected]>
Signed-off-by: Marc Zyngier <[email protected]>
Reviewed-by: Christoffer Dall <[email protected]>
Signed-off-by: Christoffer Dall <[email protected]>