avcodec/vc1_block: Fix invalid shift with rangeredfrm

Fixes: left shift of negative value -7
Fixes: 16959/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_WMV3_fuzzer-5200360825683968

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

libavcodec/vc1_block.c

@@ -1997,7 +1997,7 @@ static int vc1_decode_b_mb(VC1Context *v)
             v->vc1dsp.vc1_inv_trans_8x8(s->block[i]);
             if (v->rangeredfrm)
                 for (j = 0; j < 64; j++)
-                    s->block[i][j] <<= 1;
+                    s->block[i][j] *= 2;
             s->idsp.put_signed_pixels_clamped(s->block[i],
                                               s->dest[dst_idx] + off,
                                               i & 4 ? s->uvlinesize