omap3: pm: Use exported set_cr() instead of a custom one.

Remove the custom restore_control_register() and use the exported
set_cr() instead to set the system control register(SCTRL) value.

No functional change.

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