msm: camera: isp: support LPM on dualcamera

Handle LPM when one of the session goes to sleep.
when LPM enable unvote ab/ib of inative session and
vice versa.

Change-Id: I72ab333b24d7ad5ae4deafa758e7e2d92f3cc9d2
Signed-off-by: Ramesh V <ramev@codeaurora.org>