dt-bindings: mtd: mxc-nand: add i.MX25 and i.MX27 nand support

Add compatible string fsl,imx25-nand and fsl,imx27-nand (over 15 years
chips). Add one optional clocks for it because i.MX25 and i.MX27 upstream
DTS defines them.

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>
Signed-off-by: Frank Li <Frank.Li@nxp.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>

Author: nxpfrankli

Documentation/devicetree/bindings/mtd/mxc-nand.yaml

@@ -15,7 +15,9 @@ allOf:
 properties:
   compatible:
     oneOf:
-      - const: fsl,imx27-nand
+      - enum:
+          - fsl,imx25-nand
+          - fsl,imx27-nand
       - items:
           - enum:
               - fsl,imx31-nand
@@ -26,6 +28,9 @@ properties:
   interrupts:
     maxItems: 1
 
+  clocks:
+    maxItems: 1
+
 required:
   - compatible
   - reg