iio: Remove unnecessary _write_raw_get_fmt() in several hid-sensor drivers

IIO_VAL_INT_PLUS_MICRO is the default, no need to return it explicitly

Signed-off-by: Peter Meerwald <pmeerw@pmeerw.net>
Acked-by: srinivas pandruvada <srinivas.pandruvada@intel.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>