We don't want to encourage the bogus device_type usage.

The device type isn't used in the code, so we can simply remove it from
the documentation and dts files.

Boards should specify proper compatible entries instead.
Signed-off-by: NAnton Vorontsov <avorontsov@ru.mvista.com>
Acked-by: NDavid Gibson <david@gibson.dropbear.id.au>
Signed-off-by: NKumar Gala <galak@kernel.crashing.org>