staging:iio: Consolidate adt7310 and adt7410 driver

staging:iio: Consolidate adt7310 and adt7410 driver

The adt7310 is the SPI version of the adt7410, so there is no need to have a
separate driver for it. The register map layout is a bit different, i.e. the
addresses of the register differ, but the individual register layouts are
identical. We solve this by adding a small look-up table, which translates
adt7410 register addresses to ad7310 register addresses.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>