regulator: fan53555: fix up the dcdc is disabled when reboot

regulator: fan53555: fix up the dcdc is disabled when reboot

Before reboot if the DCDC is disabled,
the DCDC is still disabled after restart.
We have an method to workaround:
Use vsel pin to switch the voltage between value in FAN53555_VSEL0
and FAN53555_VSEL1. If VSEL pin is inactive, the voltage of DCDC
are controlled by FAN53555_VSEL0, when we pull vsel pin to active,
they would be controlled by FAN53555_VSEL1.
In this case, we can set FAN53555_VSEL1 to disable dcdc,
So we can make vsel pin to active to disable dcdc,
VSEL pin is inactive to enable DCDC.

Change-Id: I14c823ed11dc3369044ad2ed0b53a6027acbccd0
Signed-off-by: Elaine Zhang <zhangqing@rock-chips.com>