dt-bindings: pinctrl: document access-controllers property for stm32 HDP

HDP being functional depends on the debug configuration on the platform
that can be checked using the access-controllers property, document it.

Signed-off-by: Gatien Chevallier <gatien.chevallier@foss.st.com>
Acked-by: Rob Herring (Arm) <robh@kernel.org>
Acked-by: Linus Walleij <linusw@kernel.org>
Link: https://lore.kernel.org/r/20260226-debug_bus-v6-2-5d794697798d@foss.st.com
Signed-off-by: Alexandre Torgue <alexandre.torgue@foss.st.com>

Author: GseoC

Documentation/devicetree/bindings/pinctrl/st,stm32-hdp.yaml

@@ -27,6 +27,12 @@ properties:
   clocks:
     maxItems: 1
 
+  access-controllers:
+    minItems: 1
+    items:
+      - description: debug configuration access controller
+      - description: access controller that manages the HDP as a peripheral
+
 patternProperties:
   "^hdp[0-7]-pins$":
     type: object