chan_dahdi: Add some missing build cleanup.

........

Merged revisions 397643 from http://svn.asterisk.org/svn/asterisk/branches/12


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@397644 65c4cc65-6c06-0410-ace0-fbb531ad65f3

channels/Makefile

@@ -63,6 +63,7 @@ endif
 
 clean::
 	$(MAKE) -C misdn clean
+	rm -f dahdi/*.o dahdi/*.i
 	rm -f sip/*.o sip/*.i
 	rm -f iax2/*.o iax2/*.i
 	rm -f h323/libchanh323.a h323/Makefile.ast h323/*.o h323/*.dep