dt-bindings: reset: intel,rcu-gw: Fix intel,global-reset schema

The intel,rcu-gw binding example has an error:

Documentation/devicetree/bindings/reset/intel,rcu-gw.example.dt.yaml:
  reset-controller@e0000000: intel,global-reset: [[16, 30]] is too short

The error isn't really correct as the problem is in how the data is
encoded and the schema is not fixed up by the tooling correctly.
However, array properties should describe the elements in the array, so
lets do that which fixes the error in the process.

Fixes: b7ab0cb0 ("dt-bindings: reset: Add YAML schemas for the Intel Reset controller")
Cc: Dilip Kota <eswara.kota@linux.intel.com>
Signed-off-by: Rob Herring <robh@kernel.org>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>