slackware: sbopkg: fix multiple arguments for '-f'

If '-f' option written several times then used only latest

completions/slackware

@@ -189,6 +189,7 @@ _sbopkg()
     for (( i=${#words[@]}-1; i>0; i-- )); do
         if [[ ${words[i]} == '-f' ]]; then
             config="${words[i+1]}"
+	    break
         fi
     done