cifs: Remove obsoleted declaration for cifs_dir_open

The cifs_dir_open() have been removed since
commit 737b758c ("[PATCH] cifs: character mapping of special
characters (part 3 of 3)"), and now it is useless, so remove it.
Signed-off-by: Gaosheng Cui <cuigaosheng1@huawei.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/smb/client/cifsfs.h

@@ -106,7 +106,6 @@ extern int cifs_flush(struct file *, fl_owner_t id);
 extern int cifs_file_mmap(struct file *file, struct vm_area_struct *vma);
 extern int cifs_file_strict_mmap(struct file *file, struct vm_area_struct *vma);
 extern const struct file_operations cifs_dir_ops;
-extern int cifs_dir_open(struct inode *inode, struct file *file);
 extern int cifs_readdir(struct file *file, struct dir_context *ctx);
 
 /* Functions related to dir entries */