omxil: Pass pts as timestamp on the ducati decoder

This decoder reorders timestamps according to the frame reordering,
and thus should be given pts instead of dts. Other decoders don't
do this reordering and should be given dts.

Still to be investigated how android/stagefright handles this,
since it always seems pass pts, not dts, to decoders.

Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>