[ATM]: linux-atm-general mailing list is subscribers only

As the automated reply I got to my last ATM patch shows, the
linux-atm-general mailing list is subscribers-only.

Signed-off-by: Roland Dreier <roland@digitalvampire.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

MAINTAINERS

@@ -416,7 +416,7 @@ S:	Supported
 ATM
 P:	Chas Williams
 M:	chas@cmf.nrl.navy.mil
-L:	linux-atm-general@lists.sourceforge.net
+L:	linux-atm-general@lists.sourceforge.net (subscribers-only)
 W:	http://linux-atm.sourceforge.net
 S:	Maintained