avcodec/nvenc: fix signedness of timing fields

libavcodec/nvenc.c

@@ -2361,7 +2361,7 @@ static int nvenc_set_timestamp(AVCodecContext *avctx,
                                AVPacket *pkt)
 {
     NvencContext *ctx = avctx->priv_data;
-    int delay;
+    unsigned int delay;
     int64_t delay_time;
 
     pkt->pts = params->outputTimeStamp;

libavcodec/nvenc.h

@@ -207,7 +207,7 @@ typedef struct NvencContext
     AVFifo *output_surface_ready_queue;
     AVFifo *timestamp_list;
     // This is for DTS calculating, reset after flush
-    int64_t output_frame_num;
+    uint64_t output_frame_num;
     int64_t initial_delay_time;
 
     NV_ENC_SEI_PAYLOAD *sei_data;