NFS: Move nfs_idmap.h into fs/nfs/

This file is only used internally to the NFS v4 module, so it doesn't
need to be in the global include path.  I also renamed it from
nfs_idmap.h to nfs4idmap.h to emphasize that it's an NFSv4-only include
file.

Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
diff --git a/include/uapi/linux/nfs_idmap.h b/include/uapi/linux/nfs_idmap.h
index 8d4b1c7..038e36c 100644
--- a/include/uapi/linux/nfs_idmap.h
+++ b/include/uapi/linux/nfs_idmap.h
@@ -1,5 +1,5 @@
 /*
- * include/linux/nfs_idmap.h
+ * include/uapi/linux/nfs_idmap.h
  *
  *  UID and GID to name mapping for clients.
  *