avcodec/mfenc: fix double-free on init failure

mfenc sets FF_CODEC_CAP_INIT_CLEANUP, so calling mf_close() on
failure inside mf_init() results in a double-free.
Signed-off-by: Cameron Gutman <aicommander@gmail.com>
Signed-off-by: Martin Storsjö <martin@martin.st>

libavcodec/mfenc.c

@@ -1214,7 +1214,6 @@ static int mf_init(AVCodecContext *avctx)
                 return 0;
         }
     }
-    mf_close(avctx);
     return ret;
 }