dt-bindings: serial: rockchip: add rockchip,rk3128-uart

Add rockchip,rk3128-uart compatible string.

Signed-off-by: Johan Jonker <jbx6244@gmail.com>
Acked-by: Jamie Iles <jamie@jamieiles.com>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/4f283231-2ed4-202b-0c23-157bce0841ee@gmail.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>