constify security_path_{mkdir,mknod,symlink}

... as well as unix_mknod() and may_o_create()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/namei.c b/fs/namei.c
index 794f81d..8c97544 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2783,7 +2783,7 @@
 	return flag;
 }
 
-static int may_o_create(struct path *dir, struct dentry *dentry, umode_t mode)
+static int may_o_create(const struct path *dir, struct dentry *dentry, umode_t mode)
 {
 	int error = security_path_mknod(dir, dentry, mode, 0);
 	if (error)