avcodec/dirac_parser: Fix undefined memcpy() use

Fixes: 9d375e415486edd1a0c826f2307d89a4/asan_generic_4a5159_1577_faa333e83dacdd9e4dd322380aeed537.iss

Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/dirac_parser.c

@@ -123,7 +123,7 @@ static int dirac_combine_frame(AVCodecParserContext *s, AVCodecContext *avctx,
     DiracParseContext *pc = s->priv_data;
 
     if (pc->overread_index) {
-        memcpy(pc->buffer, pc->buffer + pc->overread_index,
+        memmove(pc->buffer, pc->buffer + pc->overread_index,
                pc->index - pc->overread_index);
         pc->index         -= pc->overread_index;
         pc->overread_index = 0;