msm: camera: isp: Avoid CGC override in ISP

In ISP, avoid CGC override to allow hardware to take care of
clock gating. This helps to save power.

Change-Id: I3accd2cbaa24fd3a14d2df7122ad203c97d4b41b
Signed-off-by: Sreesudhan Ramakrish Ramkumar <srramku@codeaurora.org>