dt-bindings: vendor-prefixes: add Sundance DSP

Sundance DSP Inc. (https://www.sundancedsp.com/) is a supplier of
high-performance DSP and FPGA processor boards and I/O modules.

Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20220509142610.128590-7-conor.dooley@microchip.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>