media: platform: mtk-mdp3: Use cmdq_pkt_create() and cmdq_pkt_destroy()

Use the cmdq_pkt_create() and cmdq_pkt_destroy() common functions
instead of implementing specific mdp3 versions.

Signed-off-by: Chun-Kuang Hu <chunkuang.hu@kernel.org>
Reviewed-by: Matthias Brugger <matthias.bgg@gmail.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Sebastian Fricke <sebastian.fricke@collabora.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>