msm: camera: Use separate mclks for main and front sensor.

Using separate mclks for main and front sensors for PiP
feature, which requires both the cameras to operate concurrently.
This change should be accompanied by a corresponding change
in the camera dtsi file which should separate the GPIO pins
for the mclk-s.

Change-Id: I1ce9d9d52e39e886be281f31bcf5e4a6f116784b
Signed-off-by: Petar Sivenov <psiven@codeaurora.org>