This adds the drums and guitar extensions for Wiimote devices.

Devices are reported as "Nintendo Wii Remote Guitar/Drums". If I ever
get my hands on "RockBand" guitars, I will try to report them via the
same interface so user-space does not have to bother which device it
deals with.

This is a rebase of the original commits 8e22ecb6 and 73f8645d.
They were reverted several years ago, since they were dependent on the
ABS_* rework of the input core. Sadly, this never worked out so these
commits were never pushed into a release. This rebase now uses the
ABS_HAT* event codes to report all pressure information.
Signed-off-by: Nicolas.Adenis-Lamarre <nicolas.adenis.lamarre@gmail.com>
(Original commits by Nicolas, adapted to v4.18 by David)
Signed-off-by: David Herrmann <dh.herrmann@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>