Fix typo in sig_pri using wrong structure name.

It is fortunate that the typo does not alter generated code since the
e->restart.channel and e->ring.channel members are in the same position.

(closes issue ASTERISK-18868)
Reported by: zvision
Patches:
      sig_pri.c.diff (License #5755) patch uploaded by zvision
........

Merged revisions 345370 from http://svn.asterisk.org/svn/asterisk/branches/1.8
........

Merged revisions 345371 from http://svn.asterisk.org/svn/asterisk/branches/10


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@345375 65c4cc65-6c06-0410-ace0-fbb531ad65f3