iio: accel: kxsd9: split out a common remove() function
This makes it possible to later split the transport mechanism
using a generic probe() and a generic remove().
Use dev_set_drvdata() and dev_get_drvdata() as a paired
accessor to operate on the abstract struct device * regardless
of the transport mechanism in use.
Signed-off-by: Linus Walleij <linus.walleij@linaro.org> Tested-by: Jonathan Cameron <jic23@kernel.org> Signed-off-by: Jonathan Cameron <jic23@kernel.org>