arm64: dts: r8a7796: Add cpuidle support for CA57 cores

Enable cpuidle (core shutdown) support for R-Car M3-W CA57 cores.

Parameters were found after evaluation by gaku.inami.xw@bp.renesas.com; they
help to keep the performance and reduce the power consumption.

Signed-off-by: Khiem Nguyen <khiem.nguyen.xt@rvc.renesas.com>
Signed-off-by: Takeshi Kihara <takeshi.kihara.df@renesas.com>
[dien.pham.ry: Apply new cpuidle parameters]
Signed-off-by: Dien Pham <dien.pham.ry@renesas.com>
Signed-off-by: Ulrich Hecht <uli+renesas@fpond.eu>
Link: https://lore.kernel.org/r/1547808474-19427-4-git-send-email-uli+renesas@fpond.eu


Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>