lavc/libx265: switch to ff_alloc_packet2

ff_alloc_packet have been deprecated, switch to use
ff_alloc_packet2.
Signed-off-by: Jun Zhao <jun.zhao@intel.com>
Reviewed-by: Derek Buitenhuis <derek.buitenhuis@gmail.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/libx265.c

@@ -294,7 +294,7 @@ static int libx265_encode_frame(AVCodecContext *avctx, AVPacket *pkt,
     for (i = 0; i < nnal; i++)
         payload += nal[i].sizeBytes;
 
-    ret = ff_alloc_packet(pkt, payload);
+    ret = ff_alloc_packet2(avctx, pkt, payload, payload);
     if (ret < 0) {
         av_log(avctx, AV_LOG_ERROR, "Error getting output packet.\n");
         return ret;