msm: camera: sensor: Fix power related issues

Put the regulator while powering down sensor, it
will be got again while powering up sensor. And,
configure the gpios to correct value, rather than
always power on the gpios.

Change-Id: I2bc1a3820bf0c1d8e09a609813bd2e3da825f41c
Signed-off-by: Depeng Shao <depengs@codeaurora.org>