dt-bindings: can: fsl,flexcan.yaml: fix compatible for i.MX35 and i.MX53

As both the i.MX35 and i.MX53 flexcan IP cores are compatible to the i.MX25,
they are listed as:

    compatible = "fsl,imx35-flexcan", "fsl,imx25-flexcan";

and:

    compatible = "fsl,imx53-flexcan", "fsl,imx25-flexcan";

in the SoC device trees.

This patch fixes the following errors, which shows up during a dtbs_check:

arch/arm/boot/dts/imx53-ard.dt.yaml: can@53fc8000: compatible: 'oneOf' conditional failed, one must be fixed:
   ['fsl,imx53-flexcan', 'fsl,imx25-flexcan'] is too long
   Additional items are not allowed ('fsl,imx25-flexcan' was unexpected)
   'fsl,imx53-flexcan' is not one of ['fsl,imx7d-flexcan', 'fsl,imx6ul-flexcan', 'fsl,imx6sx-flexcan']
   'fsl,imx53-flexcan' is not one of ['fsl,ls1028ar1-flexcan']
   'fsl,imx6q-flexcan' was expected
   'fsl,lx2160ar1-flexcan' was expected
   From schema: Documentation/devicetree/bindings/net/can/fsl,flexcan.yaml

Fixes: e5ab9aa7e4 ("dt-bindings: can: flexcan: convert fsl,*flexcan bindings to yaml")
Reported-by: Rob Herring <robh+dt@kernel.org>
Cc: Oleksij Rempel <o.rempel@pengutronix.de>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Link: https://lore.kernel.org/r/20201111130507.1560881-4-mkl@pengutronix.de
[robh: drop singular fsl,imx53-flexcan and fsl,imx35-flexcan]
Signed-off-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/net/can/fsl,flexcan.yaml

@@ -20,14 +20,17 @@ properties:
           - fsl,imx8qm-flexcan
           - fsl,imx8mp-flexcan
           - fsl,imx6q-flexcan
-          - fsl,imx53-flexcan
-          - fsl,imx35-flexcan
           - fsl,imx28-flexcan
           - fsl,imx25-flexcan
           - fsl,p1010-flexcan
           - fsl,vf610-flexcan
           - fsl,ls1021ar2-flexcan
           - fsl,lx2160ar1-flexcan
+      - items:
+          - enum:
+              - fsl,imx53-flexcan
+              - fsl,imx35-flexcan
+          - const: fsl,imx25-flexcan
       - items:
           - enum:
               - fsl,imx7d-flexcan