net: dsa: Add Lantiq / Intel DSA driver for vrx200

This adds the DSA driver for the GSWIP Switch found in the VRX200 SoC.
This switch is integrated in the DSL SoC, this SoC uses a GSWIP version
2.1, there are other SoCs using different versions of this IP block, but
this driver was only tested with the version found in the VRX200.
Currently only the basic features are implemented which will forward all
packages to the CPU and let the CPU do the forwarding. The hardware also
support Layer 2 offloading which is not yet implemented in this driver.

The GPHY FW loaded is now done by this driver and not any more by the
separate driver in drivers/soc/lantiq/gphy.c, I will remove this driver
is a separate patch. to make use of the GPHY this switch driver is
needed anyway. Other SoCs have more embedded GPHYs so this driver should
support a variable number of GPHYs. After the firmware was loaded the
GPHY can be probed on the MDIO bus and it behaves like an external GPHY,
without the firmware it can not be probed on the MDIO bus.

The clock names in the sysctrl.c file have to be changed because the
clocks are now used by a different driver. This should be cleaned up and
a real common clock driver should provide the clocks instead.

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
Signed-off-by: David S. Miller <davem@davemloft.net>