swscale/utils: Fix xInc overflow

Fixes: signed integer overflow: 2 * 1073741824 cannot be represented in type 'int'
Fixes: 67802/clusterfuzz-testcase-minimized-ffmpeg_SWS_fuzzer-6249515855183872

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpegSigned-off-by: Michael Niedermayer <michael@niedermayer.cc>

libswscale/utils.c

@@ -593,7 +593,7 @@ static av_cold int initFilter(int16_t **outFilter, int32_t **filterPos,
                 filter[i * filterSize + j] = coeff;
                 xx++;
             }
-            xDstInSrc += 2 * xInc;
+            xDstInSrc += 2LL * xInc;
         }
     }