CSID hardware on SM8250 can demux up to 4 simultaneous streams
based on virtual channel (vc) or datatype (dt).
The CSID subdevice entity now has 4 source ports that can be
enabled/disabled and thus can control which virtual channels
are enabled. Datatype demuxing not tested.

In order to keep a valid internal state of the subdevice,
implicit format propagation from the sink to the source pads
has been preserved. However, the format on each source pad
can be different and in that case it must be configured explicitly.

CSID's s_stream is called when any stream is started or stopped.
It will call configure_streams() that will rewrite IRQ settings to HW.
When multiple streams are running simultaneously there is an issue
when writing IRQ settings for one stream while another is still
running, thus avoid re-writing settings if they were not changed
in link setup, or by fully powering off the CSID hardware.
Signed-off-by: Milen Mitkov <quic_mmitkov@quicinc.com>
Reviewed-by: Robert Foss <robert.foss@linaro.org>
Tested-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Acked-by: Robert Foss <robert.foss@linaro.org>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>