irqchip: irq-msm: Introduce irq-msm driver

Prepare for irqchip_init() to initialize irq controllers. The
IRQCHIP_DECLARE macro inserts a function pointer in __irqchip_of_table
section and the kernel runs through it calling each irq controllers
initialization function - the kernel respects the parent irq controller
ordering and ensures that a parent irq controller's init function is
called prior to its child irq controllers.

This driver serves the purpose of being able to declare various irq
controllers in MSM/APQ/FSM platforms using IRQCHIP_DECLARE macro.

MPM hardware monitors certain interrupt lines on GIC and GPIO while
apps is power collapsed. It needs to be initialized right after GPIO
is initialized.

Change-Id: I3ab333dbb428932df060a682c0930f1e61ffe45b
Signed-off-by: Abhijeet Dharmapurikar <adharmap@codeaurora.org>