consolidate compat lookup_dcookie()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/include/linux/compat.h b/include/linux/compat.h
index cdec8f2..482c9e6 100644
--- a/include/linux/compat.h
+++ b/include/linux/compat.h
@@ -429,6 +429,7 @@
 asmlinkage long compat_sys_ptrace(compat_long_t request, compat_long_t pid,
 				  compat_long_t addr, compat_long_t data);
 
+asmlinkage long compat_sys_lookup_dcookie(u32, u32, char __user *, size_t);
 /*
  * epoll (fs/eventpoll.c) compat bits follow ...
  */