ARM: dts: Add phyBOARD-WEGA-AM335x rdk

phyBOARD-WEGA-AM335x represents a direct soldered
combination of a phyCORE-AM335x SoM and carrier board.

Different kind of SoM options can be connected to
the wega carrier board. So we created a separate
wega dtsi file. The final dts contains the actual
SoM on the carrier board.

WEGA carrier board features:
* ETH phy on carrier board: 1x MII
* 1x CAN
* 2x UART
* USB0 (device)
* USB1 (host)
* mSD slot

Signed-off-by: Teresa Remmet <t.remmet@phytec.de>
Signed-off-by: Tony Lindgren <tony@atomide.com>