dt-bindings: memory: Update brcmstb-memc-ddr binding with older chips

The older MIPS-based chips incorporated a memory controller with the
revision A.0.0, update the binding to list that compatible.

Signed-off-by: Florian Fainelli <[e-mail]>
Acked-by: Rob Herring (Arm) <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Krzysztof Kozlowski <[e-mail]>

Documentation/devicetree/bindings/memory-controllers/brcm,brcmstb-memc-ddr.yaml

···
         items:
           - const: brcm,brcmstb-memc-ddr-rev-b.1.x
           - const: brcm,brcmstb-memc-ddr
+      - description: Revision 0.x controllers
+        items:
+          - const: brcm,brcmstb-memc-ddr-rev-a.0.0
+          - const: brcm,brcmstb-memc-ddr
 
   reg:
     maxItems: 1