[PATCH] SECURITY_ROOTPLUG must depend on USB

The following patch lets SECURITY_ROOTPLUG depend on USB (otherwise
there are link errors since Root Plug Support needs
usb_bus_list{,_lock}):

security/Kconfig

@@ -33,7 +33,7 @@ config SECURITY_CAPABILITIES
 
 config SECURITY_ROOTPLUG
 	tristate "Root Plug Support"
-	depends on SECURITY!=n
+	depends on USB && SECURITY!=n
 	help
 	  This is a sample LSM module that should only be used as such.
 	  It prevents any programs running with egid == 0 if a specific