[media] vb2: set timestamp when using write()

[media] vb2: set timestamp when using write()

When using write() to write data to an output video node the vb2 core
should set timestamps if V4L2_BUF_FLAG_TIMESTAMP_COPY is set. Nobody
else is able to provide this information with the write() operation.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Acked-by: Pawel Osciak <pawel@osciak.com>
Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>