irqchip/gic-v4: Add VLPI configuration interface

Add the required interfaces to map, unmap and update a VLPI.

Reviewed-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>