fsnotify: update gfp/slab.h includes

Implicit slab.h inclusion via percpu.h is about to go away.  Make sure
gfp.h or slab.h is included as necessary.
Signed-off-by: NTejun Heo <tj@kernel.org>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Eric Paris <eparis@redhat.com>
Signed-off-by: NEric Paris <eparis@redhat.com>

fs/notify/fanotify/fanotify_user.c

@@ -10,6 +10,7 @@
 #include <linux/poll.h>
 #include <linux/security.h>
 #include <linux/syscalls.h>
+#include <linux/slab.h>
 #include <linux/types.h>
 #include <linux/uaccess.h>
 

fs/notify/vfsmount_mark.c

@@ -22,7 +22,6 @@
 #include <linux/module.h>
 #include <linux/mount.h>
 #include <linux/mutex.h>
-#include <linux/slab.h>
 #include <linux/spinlock.h>
 #include <linux/writeback.h> /* for inode_lock */