KVM: arm64: GICv4.1: Expose HW-based SGIs in debugfs

The vgic-state debugfs file could do with showing the pending state
of the HW-backed SGIs. Plug it into the low-level code.

Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Zenghui Yu <yuzenghui@huawei.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Link: https://lore.kernel.org/r/20200304203330.4967-24-maz@kernel.org