ARM: dts: am335x-igep0033: switch to new cpsw switch drv

The dual_mac mode has been preserved the same way between legacy and new
driver, and one port devices works the same as 1 dual_mac port - it's safe
to switch drivers.

So, switch am335x-igep0033 to use new cpsw switch driver. Those boards have
or 2 Ext. port wired and configured in dual_mac mode by default, or only 1
Ext. port.

Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>