V4L/DVB (8011): em28xx: enable DVB for HVR-900

em28xx-cards.c
 - DVB support is supposed to be enabled for the first generation HVR-900.
   This device was confirmed with DVB by mkrufky when we did the original work
   in April, but I guess we forgot to set the flag.

Signed-off-by: Devin Heitmueller <devin.heitmueller@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>