spi: dw-apb-ssi: Integrate Renesas RZ/N1 SPI controller

Originally, the Renesas RZ/N1 SPI Controller DT bindings were not
integrated in the main DT bindings for the Synopsys DesignWare
Synchronous Serial Interface, but in its own file, as the RZ/N1
controller has additional registers for software CS control and DMA.

As so far DMA is not supported on RZ/N1, and json-schema can handle any
possible differences fine, integrate the RZ/N1 compatible values in the
main DT bindings for the Synopsys DW SSI.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/aef15aa119ed02487ded4691141678bc1040c3b4.1620301936.git.geert+renesas@glider.beSigned-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/spi/renesas,rzn1-spi.txt

-Renesas RZ/N1 SPI Controller
-
-This controller is based on the Synopsys DW Synchronous Serial Interface and
-inherits all properties defined in snps,dw-apb-ssi.txt except for the
-compatible property.
-
-Required properties:
-- compatible : The device specific string followed by the generic RZ/N1 string.
-   Therefore it must be one of:
-   "renesas,r9a06g032-spi", "renesas,rzn1-spi"
-   "renesas,r9a06g033-spi", "renesas,rzn1-spi"

Documentation/devicetree/bindings/spi/snps,dw-apb-ssi.yaml

@@ -67,6 +67,12 @@ properties:
         const: baikal,bt1-sys-ssi
       - description: Canaan Kendryte K210 SoS SPI Controller
         const: canaan,k210-spi
+      - description: Renesas RZ/N1 SPI Controller
+        items:
+          - enum:
+              - renesas,r9a06g032-spi # RZ/N1D
+              - renesas,r9a06g033-spi # RZ/N1S
+          - const: renesas,rzn1-spi   # RZ/N1
 
   reg:
     minItems: 1