pmdomain: renesas: rcar-sysc: Add R-Car M3-W power-off delay quirk

R-Car M3-W needs a delay of 1 µs before powering off the A3IR and A3VC
power domains. Add support for this using a new flag, which indicates
that a power area is subject to this quirk.

Inspired by a patch in the BSP by Dien Pham.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Link: https://lore.kernel.org/r/ecbc3465c598084c904dd3714e2894463094ed9a.1713348705.git.geert+renesas@glider.be
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

pmdomain: renesas: rcar-sysc: Remove rcar_sysc_nullify() helper

There are no more users left of the rcar_sysc_nullify() helper, so it
can be removed.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Link: https://lore.kernel.org/r/ad61b09283cc8a9cf93a5ea9fffd1cb283b9db92.1713348705.git.geert+renesas@glider.be
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

pmdomain: Rename the genpd subsystem to pmdomain

It has been pointed out that naming a subsystem "genpd" isn't very
self-explanatory and the acronym itself that means Generic PM Domain, is
known only by a limited group of people.

In a way to improve the situation, let's rename the subsystem to pmdomain,
which ideally should indicate that this is about so called Power Domains or
"PM domains" as we often also use within the Linux Kernel terminology.

Suggested-by: Rafael J. Wysocki <rafael@kernel.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Heiko Stuebner <heiko@sntech.de>
Acked-by: Rafael J. Wysocki <rafael@kernel.org>
Acked-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20230912221127.487327-1-ulf.hansson@linaro.org