Migrate Xenomai to the new infrastructure

Xenomai used to have commented out devices to be created in the device
table that the user had to uncomment. Use the new infrastructure to do
just that.

Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Acked-by: Thomas De Schampheleire <thomas.de.schampheleire@gmail.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>