vty: cleanup logging functions

* remove unused parameter from logging_vty_add_cmds()
* mark log level descriptors static
* change internal static function int check_log_to_target() to more
  appropriate bool should_log_to_target()
* deprecate log_vty_command_*() from public API as it should only be
  used by logging_vty_add_cmds()

Change-Id: I0e9ddd7ba3ce211302d99a3494eb408907a2916e
Related: OS#71
diff --git a/src/vty/logging_vty.c b/src/vty/logging_vty.c
index 7bb79b8..7ec212e 100644
--- a/src/vty/logging_vty.c
+++ b/src/vty/logging_vty.c
@@ -737,7 +737,7 @@
 	return 1;
 }
 
-void logging_vty_add_cmds(const struct log_info *cat)
+void logging_vty_add_cmds()
 {
 	install_element_ve(&enable_logging_cmd);
 	install_element_ve(&disable_logging_cmd);
@@ -750,8 +750,8 @@
 	install_element_ve(&logging_set_category_mask_old_cmd);
 
 	/* Logging level strings are generated dynamically. */
-	logging_level_cmd.string = log_vty_command_string(cat);
-	logging_level_cmd.doc = log_vty_command_description(cat);
+	logging_level_cmd.string = log_vty_command_string();
+	logging_level_cmd.doc = log_vty_command_description();
 	install_element_ve(&logging_level_cmd);
 	install_element_ve(&show_logging_vty_cmd);
 	install_element_ve(&show_alarms_cmd);