kevent: fix build error if CONFIG_KOBJECT_UEVENT is not selected.

Thanks to Serge Hallyn <serue@us.ibm.com> for pointing this out.
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>

lib/kobject_uevent.c

@@ -168,7 +168,7 @@ core_initcall(kobject_uevent_init);
 
 #else
 static inline int send_uevent(const char *signal, const char *obj,
-			      const void *buf, int buflen, int gfp_mask)
+			      char **envp, int gfp_mask)
 {
 	return 0;
 }