avdevice/iec61883: #if unused code away, fix -O0 compilation

iec61883_parse_queue_hdv() is only called when the mpegts-demuxer
is available and can be optimized away when not. Yet this
optimization is not a given and it fails with e.g. GCC 11 when
using -O0 in which case one will get a compilation error
because the call to the unavailable avpriv_mpegts_parse_packet()
is not optimized away. Therefore #if the offending code away
in this case.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>

libavdevice/iec61883.c

@@ -220,6 +220,7 @@ static int iec61883_parse_queue_dv(struct iec61883_data *dv, AVPacket *pkt)
 
 static int iec61883_parse_queue_hdv(struct iec61883_data *dv, AVPacket *pkt)
 {
+#if CONFIG_MPEGTS_DEMUXER
     DVPacket *packet;
     int size;
 
@@ -235,7 +236,7 @@ static int iec61883_parse_queue_hdv(struct iec61883_data *dv, AVPacket *pkt)
         if (size > 0)
             return size;
     }
-
+#endif
     return -1;
 }