soc: renesas: rcar-rst: Add support for R-Car V4M

Add support for the R-Car V4M (R8A779H0) SoC to the R-Car RST driver.

Signed-off-by: Duy Nguyen <duy.nguyen.rh@renesas.com>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Link: https://lore.kernel.org/r/13dc9f014e27db5092b3cc23edddf4b5e01a6645.1706194617.git.geert+renesas@glider.be