media/v4l2_m2m: In buffered mode run jobs if either port is streaming

In order to get the intended behaviour of the stateful video
decoder API where only the OUTPUT queue needs to be enabled and fed
buffers in order to get the SOURCE_CHANGED event that configures the
CAPTURE queue, we want the device to run should either queue be
streaming.

Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>