soc: renesas: r8a779a0-sysc: Add r8a779a0 support

Add support for R-Car V3U (R8A779A0) SoC power areas and register
access, because register specification differs from R-Car Gen2/3.

Inspired by patches in the BSP by Tho Vu.

Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Link: https://lore.kernel.org/r/1599810232-29035-5-git-send-email-yoshihiro.shimoda.uh@renesas.com


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