KVM: arm/arm64: GICv4: Use pending_last as a scheduling hint

When a vPE exits, the pending_last flag is set when there are pending
VLPIs stored in the pending table. Similarily, this flag will be set
when a doorbell interrupt fires, as it indicates the same condition.

Let's update kvm_vgic_vcpu_pending_irq() to account for that
flag as well, making a vcpu runnable when set.

Acked-by: Christoffer Dall <cdall@linaro.org>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>