V4L/DVB: remove obsolete conditionalizing on DVB_DIBCOM_DEBUG

As pointed by Christoph Egger <siccegge@stud.informatik.uni-erlangen.de>,

The config Option DVB_DIBCOM_DEBUG was dropped while removing the dibusb
driver in favor of dvb-usb in 2005. However it remaind existant at some
places of the kernel config.

Instead of just removing the debug capability, the better is to just remove
the bad dependency, making the modprobe function always visible.

Thanks-to: Christoph Egger <siccegge@stud.informatik.uni-erlangen.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>