avfilter: Add missing emms_c when needed

Arch specific calls should have an emms_c following to keep the cpu
state consistent.

Reported-By: wm4
CC: libav-stable@libav.org

libavfilter/af_volume.c

@@ -278,6 +278,8 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *buf)
         }
     }
 
+    emms_c();
+
     if (buf != out_buf)
         av_frame_free(&buf);
 

libavfilter/vf_gradfun.c

@@ -118,6 +118,7 @@ static void filter(GradFunContext *ctx, uint8_t *dst, uint8_t *src, int width, i
         ctx->filter_line(dst + y * dst_linesize, src + y * src_linesize, dc - r / 2, width, thresh, dither[y & 7]);
         if (++y >= height) break;
     }
+    emms_c();
 }
 
 static av_cold int init(AVFilterContext *ctx)

libavfilter/vf_hqdn3d.c

@@ -147,6 +147,7 @@ static void denoise_depth(HQDN3DContext *s,
     else
         denoise_temporal(src, dst, frame_ant,
                          w, h, sstride, dstride, temporal, depth);
+    emms_c();
 }
 
 #define denoise(...) \