V4L/DVB (6320): v4l core: remove the unused .hardware V4L1 field

struct video_device used to define a .hardware field. While
initialized on severl drivers, this field is never used inside V4L.
However, drivers using it need to include the old V4L1 header.

This seems to cause compilation troubles with some random configs.
Better just to remove it from all drivers.

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