This moves device data out of the driver into device files. However, a
_single_ device file contains data for _several mice_ at the same time.
The reason for this is that different mice by SinoWealth may use the
same VID:PID pair. This is unfortunate, as we only allow a single
device file a given VID:PID pair.
Also move `sinowealth_led_format` enum into a header file and rename
its constants to fit in outside of the driver.
