Add PRCM IRQ entry.  This is needed for I/O wakeup support.
Signed-off-by: Keerthy <j-keerthy@ti.com>
[paul@pwsan.com: added I/O wakeup note in commit description]
Reviewed-by: Paul Walmsley <paul@pwsan.com>
Signed-off-by: Paul Walmsley <paul@pwsan.com>