MAINTAINERS: add davem in NETWORKING DRIVERS

"./scripts/get_maintainer.pl -f" does not actually show us David as the
maintainer of drivers/net directories such as team, bonding, phy or dsa.
Adding him in an M: entry of NETWORKING DRIVERS fixes this.
Signed-off-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

MAINTAINERS

@@ -9733,6 +9733,7 @@ W:	https://fedorahosted.org/dropwatch/
 F:	net/core/drop_monitor.c
 
 NETWORKING DRIVERS
+M:	"David S. Miller" <davem@davemloft.net>
 L:	netdev@vger.kernel.org
 W:	http://www.linuxfoundation.org/en/Net
 Q:	http://patchwork.ozlabs.org/project/netdev/list/