ARM: dts: nuvoton: Add OHCI node

The EHCI peripheral already exists in the devicetree, but the hardware
also supports a discrete OHCI unit on the same USB PHY. Generic OHCI
works fine for this device already and has been tested on real hardware.

Signed-off-by: William A. Kennington III <william@wkennington.com>
Link: https://patch.msgid.link/20250401233409.3215091-1-william@wkennington.com
Signed-off-by: Andrew Jeffery <andrew@codeconstruct.com.au>