dt-bindings: riscv: cpus: Add AMD MicroBlaze V 64bit compatible

32bit version has been added by commit 4a6b93f562 ("dt-bindings: riscv:
cpus: Add AMD MicroBlaze V compatible") but 64bit version also exists and
should be covered by binding too.

Signed-off-by: Michal Simek <michal.simek@amd.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>

Documentation/devicetree/bindings/riscv/cpus.yaml

@@ -45,6 +45,7 @@ properties:
       - items:
           - enum:
               - amd,mbv32
+              - amd,mbv64
               - andestech,ax45mp
               - canaan,k210
               - sifive,bullet0