V4L/DVB (7846): Re-creates VIDEO_TUNER

VIDEO_TUNER is responsible for compilation of tuners.ko module. This were the
previous behaviour before the creation of MEDIA_TUNER.

Before this patch, tuner.ko were created even for drivers that don't need a
tuner (like webcam drivers).

Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>