msm-camera: add support for cx_ipeak

camera drivers need to vote when moving to turbo clock
and unvote when moving out of turbo. cx_ipeak driver
then makes sure to limit the current drawn from cx
based on this vote. This dirver provides common utility
functions to track vote and unvote.

Change-Id: I34d860003518924ab3233d8de24ccdb11f513f7e
Signed-off-by: Srikanth Uyyala <suyyala@codeaurora.org>