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>