media: sun6i-csi: Add extra checks to the interrupt routine

Check against the enabled bits and make sure capture is running before
serving an interrupt, to add extra safety in the process.

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>