dnotify: move dir_notify_enable declaration

Move dir_notify_enable declaration to where it belongs -- dnotify.h .

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Eric Paris <eparis@redhat.com>
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index d24f761f..7b983db 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -44,6 +44,7 @@
 #include <linux/times.h>
 #include <linux/limits.h>
 #include <linux/dcache.h>
+#include <linux/dnotify.h>
 #include <linux/syscalls.h>
 #include <linux/vmstat.h>
 #include <linux/nfs_fs.h>