avcodec/atrac3plusdec: Free mdct contexts at the end

Fixes memleak
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/atrac3plusdec.c

@@ -72,6 +72,9 @@ static av_cold int atrac3p_decode_close(AVCodecContext *avctx)
     av_freep(&ctx->ch_units);
     av_freep(&ctx->fdsp);
 
+    ff_mdct_end(&ctx->mdct_ctx);
+    ff_mdct_end(&ctx->ipqf_dct_ctx);
+
     return 0;
 }