net/vsc9953: Add driver for Vitesse VSC9953 L2 Switch IP

This patch adds a driver for VSC9953 L2 Switch. This Vitesse IP
is integrated in Freescale T1040 and T1020 SoCs.
The L2 switch has 10 Ethernet ports: 2 internal fixed-links
(ports 8 and 9) at 2.5 Gbps and and 8 external ports at 1 Gbps.
The external ports may be connected to PHYs over QSGMII and SGMII.

Commands have also been added to enable/disable a port and to
check a port's link speed, duplexity and status. The commands are:

ethsw port <port_nr> enable|disable - enable/disable an l2 switch port
ethsw port <port_nr> show - show an l2 switch port's configuration

port_nr=0..9; use "all" for all ports

For more detailse please see doc/README.t1040-l2switch

Signed-off-by: Codrin Ciubotariu <codrin.ciubotariu@freescale.com>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>
Reviewed-by: York Sun <yorksun@freescale.com>