dt-bindings: pwm: renesas-tpu: Correct example TPU register block size

The Timer Pulse Unit on R-Mobile A1 has registers that lie outside the
declared register block.  Enlarge the register block size to fix this.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Simon Horman <simon.horman@netronome.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>