omxbufferpool: Update memory size for output buffer of dmabuf mode
omxbufferpool: Update memory size for output buffer of dmabuf mode

Update memory size of output buffer to match with actual plane size
of OMX (stride x sliceheight) instead of stride x sliceheight of GStreamer
as before. This updated size is similar as on no-copy mode and fix for issue:
memory size and offset in Metadata is different.

refs #118964
Signed-off-by: Thao Luong <ef4308e16b91b9bcf00aabc74dbe961cf8111f94@rvc.renesas.com>

renesas-rcar/gst-omx,renesas-rcar/gst-omx,renesas-rcar/gst-omx