iio: mma8452: add support for MMA8451Q

This adds support for this series' 14 bit accelerometer chip, MMA8451Q.
It's datasheet is available at the vendor's website:

https://cache.freescale.com/files/sensors/doc/data_sheet/MMA8451Q.pdf



Signed-off-by: Martin Kepplinger <martin.kepplinger@theobroma-systems.com>
Signed-off-by: Christoph Muellner <christoph.muellner@theobroma-systems.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>