Add module_load permission to class system

The "module_load" permission has been recently added to the "system"
class (kernel 4.7).

The following patch updates the Reference Policy so that the new
permission can be used to create SELinux policies.

Signed-off-by: Guido Trentalancia <guido@trentalancia.net>

policy/flask/access_vectors

@@ -448,6 +448,7 @@ class system
 	syslog_mod
 	syslog_console
 	module_request
+	module_load
 
 	# these are overloaded userspace
 	# permissions from systemd