source might make wrong assumptions about, for instance,
video timings.

Logic is added to correctly get the sync signal based on the available displays
in the DIGIT channel. The source is set only if both VENC and HDMI are supported.

Signed-off-by: Ricardo Neri <ricardo.neri@ti.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
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