input: sensors: add MPU6050 batching support

Update MPU6050 driver to add "set latency" and "flush"
interface, with these new interface sensor can run in
batching mode, a sensor in batching mode will buffer
sensor events into its internal FIFO and process them
in batch.

Change-Id: I71906f966e73c8134e22b425fcb613e015ee0712
Signed-off-by: Bingzhe Cai <bingzhec@codeaurora.org>