iio: Add Freescale MPL115A2 pressure / temperature sensor driver

I2C-controlled sensor with 10-bit pressure and temperature measurement

datasheet: http://cache.freescale.com/files/sensors/doc/data_sheet/MPL3115A2.pdf



v2:
* use devm_iio_device_register()

Signed-off-by: Peter Meerwald <pmeerw@pmeerw.net>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>