Revert "omap4-common: release st_wake_lock after 5s"

This reverts commit 76caf5b3c0a2904149615d6ca1db0355fa0e79df.

The real fix for the st_wake_lock is contained in the commit
"OMAP4: ST: Disabling UART if ldisc not installed.", which also
allows the L4 powerdomain to go to sleep.

Change-Id: Idba5f9a83c83c880aeed91ebcdc72fe0d319189d