iio: accel: kxcjk-1013: Refactor configuration registers into struct

Most Kionix accelerometers seem to use fairly consistent register bits,
but the register addresses are not necessarily the same. This is already
partially the case for the KXTF9 (added in commit 1540d010
("iio: accel: kxcjk1013: add support for KXTF9")), which has some
registers at different addresses.

However, it's even much worse for the KX023-1025. All register bits
used by the kxcjk-1013 driver seem to be fully compatible with KX023,
but it has most registers at totally different addresses.

In preparation to add support for KX023-1025, move the fixed register
addresses into a struct so we can change them for KX023 more easily.

Cc: Michał Mirosław <mirq-linux@rere.qmqm.pl>
Cc: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Stephan Gerhold <stephan@gerhold.net>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>