media: sun8i-a83t-mipi-csi2: Require both pads to be connected for streaming

media: sun8i-a83t-mipi-csi2: Require both pads to be connected for streaming

[ Upstream commit 8985fc724ba89d9b00694304b3f9faf69f4073d0 ]

The bridge needs both its pads connected to be able to stream data.
Enforcing this is useful to produce an error when no sensor is
connected.

Fixes: 576d196c522b ("media: sunxi: Add support for the A83T MIPI CSI-2 controller")
Signed-off-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>