ext/ogg/gstoggdemux.c: Fix seeking performance in the case where a non-header packet has a 0 granulepos (busted theor...

Original commit message from CVS:
* ext/ogg/gstoggdemux.c: (gst_ogg_pad_submit_packet):
Fix seeking performance in the case where a non-header
packet has a 0 granulepos (busted theora case).
Fixes #341719