[list] Fix typographical error from previous commit

Fix typographical error from commit ea631f6 ("[list] Add
list_first_entry()").  The symptom was PXELINUX 3.86 causing a stack
overflow under VMware.

Tested-by: Shao Miller <shao.miller@yrdsb.edu.on.ca>
Signed-off-by: Shao Miller <shao.miller@yrdsb.edu.on.ca>
Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/net/infiniband.c

 struct ib_device * last_opened_ibdev ( void ) {
 	struct ib_device *ibdev;
 
-	ibdev = list_first_entry ( &open_ib_devices, struct ib_device, list );
+	ibdev = list_first_entry ( &open_ib_devices, struct ib_device,
+				   open_list );
 	if ( ! ibdev )
 		return NULL;
 

src/net/netdevice.c

 	struct net_device *netdev;
 
 	netdev = list_first_entry ( &open_net_devices, struct net_device,
-				    list );
+				    open_list );
 	if ( ! netdev )
 		return NULL;