encoder: fix regression since we added encoder input fourcc

if you think '21VN' is magic, 0 can be used instead; i remember yami treat fourcc:0 as default/NV12.

in my local version, I add construct function for VideoFrameRawData

typedef struct VideoFrameRawData{
    VideoDataMemoryType memoryType;
    uint32_t width;
    uint32_t height;
    uint32_t pitch[3];
    uint32_t offset[3];
    uint32_t fourcc;
    uint32_t size;
    intptr_t handle;        // planar data has one fd for now, raw data also uses one pointer (+ offset)
    uint32_t internalID; // internal identification for image/surface recycle
#ifndef __ENABLE_CAPI__
         VideoFrameRawData():width(0), height(0), fourcc(0), size(0), handle(0), internalID(0) {
        };
#endif
}VideoFrameRawData;