arm64: dts: rockchip: add USB-C support for ROCK 5B+

Add hardware description for the USB-C port in the Radxa ROCK 5 Model B+
This describes the OHCI, EHCI and XHCI USB parts, but not yet the DisplayPort
AltMode, since the bindings for that are not yet upstream.

Support for the ROCK 5B is prepared, but not exposed at the moment,
since it results in unreliable boot behavior due to hard resets killing
the supply voltage. Some further investigation and fixes in the kernel's
Type-C Port Manager (TCPM) state machine is needed before exposing the
port. The ROCK 5B+ has a dedicated port for powering the board and thus
is not affected.

Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>