dt-bindings: mfd: syscon: Drop hwlocks

Apparently there is no in-tree DTS syscon node having hwlocks, so drop
the property to simplify the binding.

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

Documentation/devicetree/bindings/mfd/syscon.yaml

···
   resets:
     maxItems: 1
 
-  hwlocks:
-    maxItems: 1
-    description:
-      Reference to a phandle of a hardware spinlock provider node.
-
 required:
   - compatible
   - reg