Support for Maltron L90 keyboard media keys

The USB report descriptor sent by the Maltron L90 keyboard is invalid,
causing the media key reports not to be accepted.

This patch adds a driver which uses a report fixup to replace the
descriptor.

Signed-off-by: William Whistler <wtbw@wtbw.co.uk>
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>