arm64: dts: r8a7796: Upgrade to PSCI v1.0 to support Suspend-to-RAM

>From PSCI v1.0, Suspend-to-RAM is supported via SYSTEM_SUSPEND PSCI
function call. Hence, upgrade PSCI version for R-Car M3-W to support
Suspend-to-RAM.

The Suspend-to-RAM is highly dependent on ARM Trusted Firwmare support
since necessary callback functions will be registered after a query
to ARM Trusted Firmware about SYSTEM_SUSPEND support.

Since PSCI v1.0 is backward compatible with PSCI v0.2, CPU Hotplug and
CPUIdle should be able to work normally with this change.

Signed-off-by: Khiem Nguyen <khiem.nguyen.xt@renesas.com>
Signed-off-by: Takeshi Kihara <takeshi.kihara.df@renesas.com>
[geert: Keep "arm,psci-0.2"]
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>