soc: renesas: rcar-sysc: add R8A7792 support

Add support for R-Car V2H (R8A7792) SoC power areas to the SYSC driver.

Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>