iio: magnetometer: ak8975: add AK09116 support

Add additional AK09116 to the magnetometer driver which has the same
register mapping and scaling as the AK09112 device.

Signed-off-by: Matt Ranostay <matt.ranostay@konsulko.com>
Link: https://lore.kernel.org/r/20210825020738.35877-1-matt.ranostay@konsulko.com


Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>