MAINTAINERS: remove 3c505

This driver was removed by commit 0e245dba (drivers/net: delete the 3Com
3c505/3c507 intel i825xx support).

Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Philip Blundell <philb@gnu.org>
Cc: netdev@vger.kernel.org
Signed-off-by: Cesar Eduardo Barros <cesarb@cesarb.net>
Signed-off-by: David S. Miller <davem@davemloft.net>