cifs: mark CONFIG_CIFS_NFSD_EXPORT as BROKEN

This does not work properly with CIFS as current servers do not
enable support for the FILE_OPEN_BY_FILE_ID on SMB NTCreateX
and not all NFS clients handle ESTALE.

For now, it just plain doesn't work. Mark it BROKEN to discourage
distros from enabling it.
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>

fs/cifs/Kconfig

@@ -156,6 +156,6 @@ config CIFS_ACL
 
 config CIFS_NFSD_EXPORT
 	  bool "Allow nfsd to export CIFS file system (EXPERIMENTAL)"
-	  depends on CIFS && EXPERIMENTAL
+	  depends on CIFS && EXPERIMENTAL && BROKEN
 	  help
 	   Allows NFS server to export a CIFS mounted share (nfsd over cifs)