[media] v4l: ti-vpe: retain v4l2_buffer flags for captured buffers

The dequed CAPTURE_MPLANE type buffers don't contain the flags that the
originally queued OUTPUT_MPLANE type buffers have. This breaks compliance.

Copy the source v4l2_buffer flags to the destination v4l2_buffer flags before
they are dequed.

Reviewed-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Archit Taneja <archit@ti.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>