dt-bindings: nvmem: imx-ocotp: Update i.MX 8M compatibles

DTSes with new i.MX 8M SoCs use two compatibles so update the binding to
fix dtbs_check warnings like:

  arch/arm64/boot/dts/freescale/imx8mn-evk.dt.yaml: efuse@30350000: compatible:1: 'syscon' was expected
    From schema: Documentation/devicetree/bindings/nvmem/imx-ocotp.yaml

  arch/arm64/boot/dts/freescale/imx8mn-evk.dt.yaml: efuse@30350000:
    compatible: ['fsl,imx8mn-ocotp', 'fsl,imx8mm-ocotp', 'syscon'] is too long

  arch/arm64/boot/dts/freescale/imx8mn-evk.dt.yaml: efuse@30350000:
    compatible: Additional items are not allowed ('syscon' was unexpected)
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/nvmem/imx-ocotp.yaml

@@ -19,7 +19,8 @@ allOf:
 
 properties:
   compatible:
-    items:
+    oneOf:
+      - items:
           - enum:
               - fsl,imx6q-ocotp
               - fsl,imx6sl-ocotp
@@ -31,8 +32,15 @@ properties:
               - fsl,imx7ulp-ocotp
               - fsl,imx8mq-ocotp
               - fsl,imx8mm-ocotp
+          - const: syscon
+      - items:
+          - enum:
               - fsl,imx8mn-ocotp
+              # i.MX8MP not really compatible with fsl,imx8mm-ocotp, however
+              # the code for getting SoC revision depends on fsl,imx8mm-ocotp
+              # compatible.
               - fsl,imx8mp-ocotp
+          - const: fsl,imx8mm-ocotp
           - const: syscon
 
   reg: