dt-bindings: thermal: rcar-gen3-thermal: update register size in example

The datasheet has been expanded with more registers and the DT files
have been updated with the new size. This change updates the example so
writing new DT files can use the enhanced driver which uses the new
registers.

Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
[robh: s/have/has/, s/enchanted/enhanced/]
Signed-off-by: Rob Herring <robh@kernel.org>