V4L/DVB (4631): Av7110: remove V4L2_CAP_VBI_CAPTURE flag

Implement fix suggested by Michael Hunold for a bug reported
by Philipp Matthias Hahn: Starting "kdetv" on a Siemens DVB-C 1.x
produced an oops because kdetv opened "/dev/vbi0".
Remove the V4L2_CAP_VBI_CAPTURE flag because it does not work with
this type of hardware anyway.

Signed-off-by: Oliver Endriss <o.endriss@gmx.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>