msm: camera: sensor: Add support to vote for PWM mode

Camera image sensor needs to vote to BoB regualtor to switch into
PWM operation mode in order to reduce analog voltage noise. This
change votes for PWM operational mode switch at the time of power on
camera image sensor and Auto mode switch at the time of power off.

Change-Id: Iea3e5642e3ef6a06b0916a36fa118e22a4c48573
Signed-off-by: Jigarkumar Zala <jzala@codeaurora.org>