mpm-of: Support multiple mpm pin mapping to same gic interrupt

Currently one gic interrupt is mapped to one mpm pin.
Support multiple mpm pins to get enabled with single irq
with client drivers using enable_irq_wake API.

Change-Id: Iea575079c24ed0986b74fb6e86c7b8100474f19e
Signed-off-by: Maulik Shah <mkshah@codeaurora.org>