dt-bindings: mailbox: fsl,mu: Add i.MX94 compatible

Add compatible string "fsl,imx94-mu" for the i.MX94 chip, which is backward
compatible with i.MX95. Set it to fall back to "fsl,imx95-mu".

Signed-off-by: Frank Li <Frank.Li@nxp.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Jassi Brar <jassisinghbrar@gmail.com>

Author: nxpfrankli

Documentation/devicetree/bindings/mailbox/fsl,mu.yaml

@@ -54,6 +54,10 @@ properties:
               - fsl,imx8qm-mu
               - fsl,imx8qxp-mu
           - const: fsl,imx6sx-mu
+      - items:
+          - enum:
+              - fsl,imx94-mu
+          - const: fsl,imx95-mu
 
   reg:
     maxItems: 1
@@ -142,7 +146,8 @@ allOf:
       not:
         properties:
           compatible:
-            const: fsl,imx95-mu
+            contains:
+              const: fsl,imx95-mu
     then:
       patternProperties:
         "^sram@[a-f0-9]+": false