drx: add initial drx-d driver

These are the original drx-d sources, extracted from Ralph Metzler's GPL'd
ngene driver.  No modifications/cleanup have yet been made.  In fact, no
measures have been taken to see if the code even compiles.

Signed-off-by Ralph Metzler <rjkm@metzlerbros.de>
Signed-off-by: Devin Heitmueller <dheitmueller@kernellabs.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>