ARM: OMAP2+: mux: add support for PAD wakeup interrupts

ARM: OMAP2+: mux: add support for PAD wakeup interrupts

OMAP mux now parses active wakeup events from pad registers and calls
corresponding hwmod ISRs once a wakeup is detected. This is
accomplished by registering an interrupt handler for PRCM IO event,
which is raised every time the HW detects wakeups.

[paul@pwsan.com: This patch is a merge of Govindraj R's "ARM: OMAP2+:
hwmod: Add API to check IO PAD wakeup status" patch, Tero Kristo's
"ARM: OMAP2+: mux: add support for PAD wakeup interrupts" patch, and
part of Tero's "ARM: OMAP: mux: add support for selecting mpu_irq for
each wakeup pad" patch.]

Signed-off-by: Tero Kristo <t-kristo@ti.com>
Cc: Govindraj.R <govindraj.raja@ti.com>
Tested-by: Kevin Hilman <khilman@ti.com>
Reviewed-by: Kevin Hilman <khilman@ti.com>
Acked-by: Tony Lindgren <tony@atomide.com>
[paul@pwsan.com: reduced indentation level; renamed omap_hwmod function;
 improved function documentation; modified to iterate only through dynamic
 pads; modified to skip pads where idle mode doesn't enable wakeups; split
 patches]
Signed-off-by: Paul Walmsley <paul@pwsan.com>