iio: accel: bma180: BMA254 support

This adds support for the BMA254 variant of this
accelerometer. The only difference for the simple IIO
driver is that values are 12 bit and the temperature
offset differs by 1 degree.

Whilst wildcards in naming are normally frowned upon:

The cases where I have labeled variables "25x" is where the
models are identical, so as to make things easier for people
that want to add support for BMA253 and BMA255.

Cc: Peter Meerwald <pmeerw@pmeerw.net>
Cc: Oleksandr Kravchenko <o.v.kravchenko@globallogic.com>
Cc: devicetree@vger.kernel.org
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>