irqchip/gic-v4.1: Allow direct invalidation of VLPIs

Just like for INVALL, GICv4.1 has grown a VPE-aware INVLPI register.
Let's plumb it in and make use of the DirectLPI code in that case.

Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Zenghui Yu <yuzenghui@huawei.com>
Link: https://lore.kernel.org/r/20191224111055.11836-16-maz@kernel.org