media: vivid: Set vid_cap_streaming and vid_out_streaming to true

When vbi stream is started, followed by video streaming,
the vid_cap_streaming and vid_out_streaming were not being set to true,
which would cause the video stream to stop when vbi stream is stopped.
This patch allows to set vid_cap_streaming and vid_out_streaming to true.
According to Hans Verkuil it appears that these 'if (dev->kthread_vid_cap)'
checks are a left-over from the original vivid development and should never
have been there.

Signed-off-by: Vandana BN <bnvandana@gmail.com>
Cc: <stable@vger.kernel.org>      # for v3.18 and up
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>