HID: wiimote: Parse accelerometer data

Add parser functions for accelerometer data reported by the wiimote. The data is
almost always reported in the same format, so we can use a single handler.
However, an own handler function is created for each DRM-mode because when IR
and extension support is added, each of them is parsed differently.

Also set the appropriate DRM including accelerometer data on DRM requests to
actually retrieve the accelerometer data.

Data is reported to userspace as ABS_RX/Y/Z values. The values are between -500
and 500 and 0 means no acceleration. See also userspace xwiimote library for
data parsing.

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