dt-bindings: crypto: Document aspeed,ahbc property for Aspeed ACRY

The g6 DTSI already provides the property and the driver errors out if
the AHB controller's syscon can't be located, so define the property and
mark it as required.

Signed-off-by: Andrew Jeffery <andrew@codeconstruct.com.au>
Link: https://patch.msgid.link/20251211-dev-dt-warnings-all-v1-10-21b18b9ada77@codeconstruct.com.au
Signed-off-by: Rob Herring (Arm) <robh@kernel.org>

Documentation/devicetree/bindings/crypto/aspeed,ast2600-acry.yaml

@@ -30,11 +30,17 @@ properties:
   interrupts:
     maxItems: 1
 
+  aspeed,ahbc:
+    $ref: /schemas/types.yaml#/definitions/phandle
+    description:
+      A phandle to the AHB controller node, which must be a syscon
+
 required:
   - compatible
   - reg
   - clocks
   - interrupts
+  - aspeed,ahbc
 
 additionalProperties: false
 
@@ -46,4 +52,5 @@ examples:
         reg = <0x1e6fa000 0x400>, <0x1e710000 0x1800>;
         interrupts = <160>;
         clocks = <&syscon ASPEED_CLK_GATE_RSACLK>;
+        aspeed,ahbc = <&ahbc>;
     };