ARM: OMAP4: PRM: Add IO Daisychain support

IO daisychain is a mechanism that allows individual IO pads to generate
wakeup events on their own based on a switch of an input signal level.
This allows the hardware module behind the pad to be powered down, but
still have device level capability to detect IO events, and once this
happens the module can be powered back up to resume IO. See section
3.9.4 in OMAP4430 Public TRM for details.

Signed-off-by: Rajendra Nayak <rnayak@ti.com>
Signed-off-by: Vishwanath BS <vishwanath.bs@ti.com>
Signed-off-by: Tero Kristo <t-kristo@ti.com>
[paul@pwsan.com: use the shared MAX_IOPAD_LATCH_TIME declaration; renamed
 omap4_trigger_io_chain() to conform to other PRM function names;
 added kerneldoc; resolved checkpatch warnings]
Signed-off-by: Paul Walmsley <paul@pwsan.com>