dt-bindings: cache: sifive,ccache0: add a pic64gx compatible

The pic64gx use the same IP than mpfs, therefore add compatibility with
mpfs as fallback.

Signed-off-by: Pierre-Henry Moussay <[e-mail]>
Acked-by: Rob Herring (Arm) <[e-mail]>
Signed-off-by: Conor Dooley <[e-mail]>

Documentation/devicetree/bindings/cache/sifive,ccache0.yaml

···
           - const: microchip,mpfs-ccache
           - const: sifive,fu540-c000-ccache
           - const: cache
+      - items:
+          - const: microchip,pic64gx-ccache
+          - const: microchip,mpfs-ccache
+          - const: sifive,fu540-c000-ccache
+          - const: cache
 
   cache-block-size:
     const: 64