dt-bindings: dma: owl: Add compatible string for Actions Semi S500 SoC

Add a new compatible string corresponding to the DMA controller found
in the S500 variant of the Actions Semi Owl SoCs family. Additionally,
order the entries alphabetically.

Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@gmail.com>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/2bd23ef5dad5dd613006c20d714b1be3c4d38e7a.1609263738.git.cristian.ciocaltea@gmail.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>