dt-bindings: cpu: Add Renesas R9A06G032 SMP enable method.

Add a special enable method for second CA7 of the R9A06G032

Signed-off-by: Michel Pollet <michel.pollet@bp.renesas.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>