dt-bindings: soc: ti: pruss: Add dma-coherent property

Update the PRUSS schema file to include the dma-coherent property
that indicates the coherency of the IP. The PRUSS IPs on 66AK2G
SoCs do use this property.

The new added dma-coherent property is a required property _only_
for 66AK2G SoCs and is not required/applicable for other SoCs, so
the binding is backward compatible for other SoCs. This update is
being done before the corresponding dts nodes can be added for 66AK2G
SoCs.

Signed-off-by: Suman Anna <[e-mail]>
Reviewed-by: Grygorii Strashko <[e-mail]>
Reviewed-by: Rob Herring <[e-mail]>
Signed-off-by: Santosh Shilimkar <[e-mail]>

Documentation/devicetree/bindings/soc/ti/ti,pruss.yaml

···
   dma-ranges:
     maxItems: 1
 
+  dma-coherent: true
+
   power-domains:
     description: |
       This property is as per sci-pm-domain.txt.
···
 # - interrupt-controller
 # - pru
 
-if:
-  properties:
-    compatible:
-      contains:
-        enum:
-          - ti,k2g-pruss
-          - ti,am654-icssg
-          - ti,j721e-icssg
-          - ti,am642-icssg
-then:
-  required:
-    - power-domains
+allOf:
+  - if:
+      properties:
+        compatible:
+          contains:
+            enum:
+              - ti,k2g-pruss
+              - ti,am654-icssg
+              - ti,j721e-icssg
+              - ti,am642-icssg
+    then:
+      required:
+        - power-domains
+
+  - if:
+      properties:
+        compatible:
+          contains:
+            enum:
+              - ti,k2g-pruss
+    then:
+      required:
+        - dma-coherent
 
 examples:
   - |