drivers:iio:accel:mma8452: removed unwanted return statements

Removed unwanted return statements from the function
mma8452_set_freefall_mode.

Signed-off-by: Bijosh Thykkoottathil <bijosh.t@hotmail.com>
Acked-by: Martin Kepplinger <martink@posteo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>