Add support for MPL3115 NXP pressure sensor.
Tested by reading temperature and pressure:
$ cat /sys/bus/iio/devices/iio:device0/in_temp_raw
$ cat /sys/bus/iio/devices/iio:device0/in_pressure_raw
Signed-off-by: Breno Lima <breno.lima@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>