input: sensors: add enable and poll_delay handler for mpu3050 sensor driver

The kernel will create the general enable and poll_delay interfaces
in the "/sys/class/sensors/xxx" for each sensor driver using sensor
class interface.

Change-Id: I17ca9822b759ec16393a184ce6bd16458a51ff65
Signed-off-by: Oliver Wang <mengmeng@codeaurora.org>