dt-bindings: serial: Add a new compatible string for UMS512

The UMS512 also uses the same serial device with SC9836.

Signed-off-by: Chunyan Zhang <chunyan.zhang@unisoc.com>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20210928095229.233572-3-zhang.lyra@gmail.com


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