dt-bindings: power: renesas,apmu: Group tuples in cpus properties

To improve human readability and enable automatic validation, the tuples
in "cpus" properties in device nodes for Advanced Power Management Units
for AP-System Core (APMU) should be grouped using angle brackets.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20210204125542.1645925-1-geert+renesas@glider.be


Signed-off-by: Rob Herring <robh@kernel.org>