gmc: Always use edge emu

The gmc functions access more pixels than there is allocated memory.
Fixes out of array reads

Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/mpegvideo_motion.c

@@ -59,13 +59,11 @@ static void gmc1_motion(MpegEncContext *s,
 
     ptr = ref_picture[0] + (src_y * linesize) + src_x;
 
-    if(s->flags&CODEC_FLAG_EMU_EDGE){
         if(   (unsigned)src_x >= FFMAX(s->h_edge_pos - 17, 0)
            || (unsigned)src_y >= FFMAX(s->v_edge_pos - 17, 0)){
             s->vdsp.emulated_edge_mc(s->edge_emu_buffer, ptr, linesize, 17, 17, src_x, src_y, s->h_edge_pos, s->v_edge_pos);
             ptr= s->edge_emu_buffer;
         }
-    }
 
     if((motion_x|motion_y)&7){
         s->dsp.gmc1(dest_y  , ptr  , linesize, 16, motion_x&15, motion_y&15, 128 - s->no_rounding);
@@ -98,14 +96,12 @@ static void gmc1_motion(MpegEncContext *s,
 
     offset = (src_y * uvlinesize) + src_x;
     ptr = ref_picture[1] + offset;
-    if(s->flags&CODEC_FLAG_EMU_EDGE){
         if(   (unsigned)src_x >= FFMAX((s->h_edge_pos>>1) - 9, 0)
            || (unsigned)src_y >= FFMAX((s->v_edge_pos>>1) - 9, 0)){
             s->vdsp.emulated_edge_mc(s->edge_emu_buffer, ptr, uvlinesize, 9, 9, src_x, src_y, s->h_edge_pos>>1, s->v_edge_pos>>1);
             ptr= s->edge_emu_buffer;
             emu=1;
         }
-    }
     s->dsp.gmc1(dest_cb, ptr, uvlinesize, 8, motion_x&15, motion_y&15, 128 - s->no_rounding);
 
     ptr = ref_picture[2] + offset;