avcodec/mpeg4videodec: Remove use of FF_PROFILE_MPEG4_SIMPLE_STUDIO as indicator of studio profile

The profile field is changed by code inside and outside the decoder,
its not a reliable indicator of the internal codec state.
Maintaining it consistency with studio_profile is messy.
Its easier to just avoid it and use only studio_profile

Fixes: assertion failure
Fixes: ffmpeg_crash_9.avi

Found-by: Thuan Pham, Marcel Böhme, Andrew Santosa and Alexandru Razvan Caciulescu with AFLSmart
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
static av_always_inline void add_blocklist(int (*blocklist)[2], int *blocklist_length, uint8_t *fixed, int mb_x, int mb_y, int mb_xy)
{
    if (fixed[mb_xy])
        return;
    fixed[mb_xy] = MV_LISTED;
    blocklist[ *blocklist_length   ][0] = mb_x;
    blocklist[(*blocklist_length)++][1] = mb_y;
}

static av_always_inline void add_blocklist(int (*blocklist)[2], int *blocklist_length, uint8_t *fixed, int mb_x, int mb_y, int mb_xy)
{
    if (fixed[mb_xy])
        return;
    fixed[mb_xy] = MV_LISTED;
    blocklist[ *blocklist_length   ][0] = mb_x;
    blocklist[(*blocklist_length)++][1] = mb_y;
}
