selinux: Make selinux_kernfs_init_security static

Fix sparse warning:

security/selinux/hooks.c:3389:5: warning:
 symbol 'selinux_kernfs_init_security' was not declared. Should it be static?
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Acked-by: Ondrej Mosnacek <omosnace@redhat.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>

security/selinux/hooks.c

@@ -3386,8 +3386,8 @@ static int selinux_inode_copy_up_xattr(const char *name)
 
 /* kernfs node operations */
 
-int selinux_kernfs_init_security(struct kernfs_node *kn_dir,
-				 struct kernfs_node *kn)
+static int selinux_kernfs_init_security(struct kernfs_node *kn_dir,
+					struct kernfs_node *kn)
 {
 	const struct task_security_struct *tsec = current_security();
 	u32 parent_sid, newsid, clen;