irqchip/gic-v3-its: Register LPI tables with EFI config table

Upon enabling a redistributor, let's register the allocated tables
with the EFI table that tracks the memory reservations.

Tested-by: Jeremy Linton <jeremy.linton@arm.com>
Tested-by: Bhupesh Sharma <bhsharma@redhat.com>
Tested-by: Lei Zhang <zhang.lei@jp.fujitsu.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>