msm: pil: Enable/disable irq's on subsystem powerup/shutdown

The current implementation enables most IRQs when the subsystems
are registered.

This change disables these irqs for a subsystem when it is being
shutdown and enables them again on powering up. This way, we do
not need to worry about multiple interrupts during a subsystem
restart or having to deal with spurious interrupts when a subsystem
is already shutdown.

Change-Id: I2768e4efc13688ed43b80ded8a5eef98d9d6bf06
Signed-off-by: Deepak Katragadda <dkatraga@codeaurora.org>