V4L/DVB: v4l: videobuf: qbuf now uses relevant v4l2_buffer fields for OUTPUT types

According to the V4L2 specification, applications set bytesused, field and
timestamp fields of struct v4l2_buffer when the buffer is intended for
output and memory type is MMAP. This adds proper copying of those values
to videobuf_buffer so drivers can use them.

Signed-off-by: Pawel Osciak <p.osciak@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>