input: sensors: add power optimization for mmc3416x magnetic sensor

The power up/down is not handled properly. Add suspend/resume
functions and fix power ops functions issue which will enable
the sensor power by default in probe function.

CRs-fixed: 657320
Change-Id: I9796808a10245de2d0b563a56545ef82ca48bfe2
Signed-off-by: Oliver Wang <mengmeng@codeaurora.org>