Enhancement: Changed sccp_chanenl_sched_hangup_by_callid to static _sccp_chanenl_sched_hangup

git-svn-id: https://svn.code.sf.net/p/chan-sccp-b/code/trunk@5722 43c1dc8c-776e-4df2-8ef1-6e829299be21
Fix: compile error for asterisk-1.8 / asterisk-10. (Reported by Hhornung)

git-svn-id: https://svn.code.sf.net/p/chan-sccp-b/code/trunk@5723 43c1dc8c-776e-4df2-8ef1-6e829299be21