omap: pm-debug: Move common debug code to pm-debug.c

This patch moves omap2_pm_wakeup_on_timer() and pm debug entries
form pm34xx.c to pm-debug.c and export it, so that it is available
to other OMAPs

Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>