net: dsa: mv88e6xxx: Add support for ethernet switch 88E6141

The Marvell 88E6341 device is single-chip, 6-port Ethernet switch with
four integrated 10/100/1000Mbps Ethernet transceivers and one high speed
SerDes interfaces.

It belongs to the Topaz family and unlike the 88E6341 it does not have
a TCAM.

Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>
Reviewed-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Signed-off-by: David S. Miller <davem@davemloft.net>