MAINTAINERS: Add tools/net to NETWORKING [GENERAL]

Make sure patches for these tools go to the netdev list as well.

References: https://marc.info/?l=linux-kernel&m=139450284501328&w=2
Cc: David S. Miller <davem@davemloft.net>
Cc: Daniel Borkmann <dborkman@redhat.com>
Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

MAINTAINERS

@@ -6002,6 +6002,7 @@ F:	include/linux/netdevice.h
 F:	include/uapi/linux/in.h
 F:	include/uapi/linux/net.h
 F:	include/uapi/linux/netdevice.h
+F:	tools/net/
 
 NETWORKING [IPv4/IPv6]
 M:	"David S. Miller" <davem@davemloft.net>