iio: pressure: bmp280: use FIELD_GET, FIELD_PREP and GENMASK

Cleaned and simplified register values construction and extraction
converting to use FIELD_PREP and FIELD_GET macros.

Replaced hardcoded bit masks with GENMASK macro.

Signed-off-by: Angel Iglesias <ang.iglesiasg@gmail.com>
Link: https://lore.kernel.org/r/3cbe56f29c2a46bc5dc23c5b72e1b43c9207f44d.1663025017.git.ang.iglesiasg@gmail.com


Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>