add dahdi_func_write to zap_tech structure

This was supposed to be committed with r263292, the back-port
of teh DAHDI buffer policy dial string option


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.4@266140 65c4cc65-6c06-0410-ace0-fbb531ad65f3

channels/chan_dahdi.c

@@ -1047,6 +1047,7 @@ static const struct ast_channel_tech zap_tech = {
 	.fixup = dahdi_fixup,
 	.setoption = dahdi_setoption,
 	.func_channel_read = dahdi_func_read,
+	.func_channel_write = dahdi_func_write,
 };
 
 static const struct ast_channel_tech *chan_tech;