HID: Prodikeys PC-MIDI HID Driver

A specialised HID driver for the Creative Prodikeys PC-MIDI USB Keyboard.

The Prodikeys PC-MIDI is a multifunction keyboard comprising a qwerty keyboard,
multimedia keys and a touch sensitive musical keyboard.

The specialised HID driver adds full support for the musical keyboard and extra
multimedia keys which are not currently handled by the default HID driver.

The specialised HID driver interfaces with ALSA, and presents the midi keyboard
as a rawmidi device. Sustain duration, octave shifting and the midi output
channel can be read/written form userspace via sysfs.

Signed-off-by: Don Prince <dhprince-devel@yahoo.co.uk>
ALSA parts:
Acked-by: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>