ARM: dts: Add HSUSB2 EHCI Support to Logic PD DM37xx SOM-LV

The Logic PD SOM-LV has a USB Host Controller connected to 3-port
hub.  This enables the pin muxing for the host controller and
ehci-phy.

Signed-off-by: Adam Ford <aford173@gmail.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>