HID: wiimote: Parse motion+ data

Motion+ reports rotation gyro data which we report to userspace as ABS_RX/Y/Z
values. The device reports them either in fast or slow mode. We adjust the
values to get a linear scale so userspace does not need to know about slow and
fast mode.

The motion+ also reports whether an extension is connected to it. We keep track
of this value and reinitialize the extensions if an extension is plugged or
unplugged.

Signed-off-by: David Herrmann <dh.herrmann@googlemail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>