mpegtsenc: fix PMT PID calculation

445996aa51 caused the PMT PID to be
off by one.  This corrects it.

Signed-off-by: Mans Rullgard <mans@mansr.com>
(cherry picked from commit 740ad0d14d)

libavformat/mpegtsenc.c

@@ -396,7 +396,7 @@ static MpegTSService *mpegts_add_service(MpegTSWrite *ts,
     service = av_mallocz(sizeof(MpegTSService));
     if (!service)
         return NULL;
-    service->pmt.pid = ts->pmt_start_pid + ts->nb_services;
+    service->pmt.pid = ts->pmt_start_pid + ts->nb_services - 1;
     service->sid = sid;
     service->provider_name = av_strdup(provider_name);
     service->name = av_strdup(name);