irqchip/gic-v4.1: Advertise support v4.1 to KVM

Tell KVM that we support v4.1. Nothing uses this information so far.

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/20200304203330.4967-7-maz@kernel.org