dnxhdenc: fix mb_rc size

Fixes out of array access with RC_VARIANCE set to 0
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/dnxhdenc.c

@@ -235,7 +235,7 @@ static av_cold int dnxhd_init_qmat(DNXHDEncContext *ctx, int lbias, int cbias)
 
 static av_cold int dnxhd_init_rc(DNXHDEncContext *ctx)
 {
-    FF_ALLOCZ_OR_GOTO(ctx->m.avctx, ctx->mb_rc, 8160*ctx->m.avctx->qmax*sizeof(RCEntry), fail);
+    FF_ALLOCZ_OR_GOTO(ctx->m.avctx, ctx->mb_rc, 8160*(ctx->m.avctx->qmax + 1)*sizeof(RCEntry), fail);
     if (ctx->m.avctx->mb_decision != FF_MB_DECISION_RD)
         FF_ALLOCZ_OR_GOTO(ctx->m.avctx, ctx->mb_cmp, ctx->m.mb_num*sizeof(RCCMPEntry), fail);