[media] go7007: dubious one-bit signed bitfields

Because they're signed, "is_video" and "is_audio" can be 0 and -1
instead of 0 and 1 as intended.  It doesn't cause a bug, but it makes
Sparse complain:
drivers/staging/media/go7007/go7007-priv.h:94:31: error: dubious one-bit signed bitfield
drivers/staging/media/go7007/go7007-priv.h:95:31: error: dubious one-bit signed bitfield

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>