media: sun6i-csi: Only configure capture when streaming

Add a streaming element to the capture state structure to know if the
capture device is used or not. Only configure things related to output
when streaming, including the output format, irq, state (dma buffer)
and window configuration registers.

After this change, it becomes possible to use the bridge without the
capture device, which will be the case in the isp media flow.

Signed-off-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
Acked-by: Jernej Skrabec <jernej.skrabec@gmail.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>