media: mediatek: vcodec: separate decoder and encoder

Move all decoder files to folder decoder.
Move all encoder files to folder encoder.
Move common files which shared for encoder and decoder to folder common.

Change include header files and Makefile to fix build error.

Signed-off-by: Yunfei Dong <yunfei.dong@mediatek.com>
Reviewed-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>