msm: camera: sensor: Remove unrelevant power down sequence

Sensor power down is called although power up is failing. This
operation is not correct, so removing sensor power down call
in case sensor power up fails.

Change-Id: I0b6003b6e0cf99d3c29a20bbd00b1d888cf0114c
Signed-off-by: Jigarkumar Zala <jzala@codeaurora.org>