avcodec/rv10: Fix integer overflow in aspect ratio compare

Fixes: signed integer overflow: 2040 * 1187872 cannot be represented in type 'int'
Fixes: 15368/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_RV20_fuzzer-5681657136283648

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

libavcodec/rv10.c

@@ -388,9 +388,9 @@ static int rv20_decode_picture_header(RVDecContext *rv)
             // attempt to keep aspect during typical resolution switches
             if (!old_aspect.num)
                 old_aspect = (AVRational){1, 1};
-            if (2 * new_w * s->height == new_h * s->width)
+            if (2 * (int64_t)new_w * s->height == (int64_t)new_h * s->width)
                 s->avctx->sample_aspect_ratio = av_mul_q(old_aspect, (AVRational){2, 1});
-            if (new_w * s->height == 2 * new_h * s->width)
+            if ((int64_t)new_w * s->height == 2 * (int64_t)new_h * s->width)
                 s->avctx->sample_aspect_ratio = av_mul_q(old_aspect, (AVRational){1, 2});
 
             ret = ff_set_dimensions(s->avctx, new_w, new_h);