regulator: fan53555: add support for device tree and option 13 feature

Add device tree support. Add support for restoring voltage select register
from back up register. Add support for setting vsel pin by gpio output
according to device tree information. Add option to disable regulator
suspend method. Add set_voltage_time_sel to regulator_ops. Add support for
option 13's voltage range.

Change-Id: Iab9b160ff83c66f59cccedbd23d4aed7acb7d7a3
Signed-off-by: Ke Liu <keliu@codeaurora.org>