iio: mma8452: add support for FXLS8471Q

This adds support for Freescale's (now NXP's) FXLS8471Q accelerometer.

We use MMA8451Q's configuration because for what the driver supports,
FXLS8471Q is the same.

Support for FXLS8471Q's features (fast SPI interface and a larger FIFO,
among others) can be added to this driver anytime.

See it's datasheet for the details:
http://cache.nxp.com/files/sensors/doc/data_sheet/FXLS8471Q.pdf



Signed-off-by: Martin Kepplinger <martink@posteo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>