media: adds the feature of the amvdec ports are based on v4l2.[1/2]

media: adds the feature of the amvdec ports are based on v4l2.[1/2]

PD#153299:
1. amports has v4l for video decoding implemented upstream.
2. Only the decoding of h264 has been implemented at the moment.
3. the maximun resolution supports 1080p currently.
4. it is nv12 that the canvas data format of the decoder output.
5. the detailed description can be referred to wiki.
wiki: Media/The_V4L2_Amvdec_Ports_Instructions

Change-Id: Ie19311e1f44ae53b491500be9903f3d82c83b800
Signed-off-by: Nanxin Qin <nanxin.qin@amlogic.com>