sensors: add enable and poll_delay handle for kxtj9 sensor drver

Add enable and poll_delay handle functions for the kxtj9 accelerometer
driver. The system will create the general enable and poll_delay handles
in the "/sys/class/sensors/xxx/" for each sensor drvier which is using
the sensor class driver.

Change-Id: I7ff71bd554f864c62b642791222c7d575d4c6b7f
Signed-off-by: Jie Cheng <rockiec@codeaurora.org>