switch vfs_mkdir() and ->mkdir() to umode_t

vfs_mkdir() gets int, but immediately drops everything that might not
fit into umode_t and that's the only caller of ->mkdir()...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/mm/shmem.c b/mm/shmem.c
index c58594c..b8a8ddf 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1489,7 +1489,7 @@
 	return error;
 }
 
-static int shmem_mkdir(struct inode *dir, struct dentry *dentry, int mode)
+static int shmem_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
 {
 	int error;