msm: camera: Sensor power down sequence

During sensor probe, all sensors compiled for the platform is probed.
Sensor stop stream need not be called during power down of probe
sequence. If stop stream is called, camera preview start up may
not work due to wrong I2C write from other sensors.

Change-Id: I00a324773817e3256d2255994b1469cd3a9f6837
Signed-off-by: Sreesudhan Ramakrish Ramkumar <srramku@codeaurora.org>