pmdomain: renesas: rcar: Remove obsolete nullify checks

All nullify users and helpers were removed, but the R-Car SYSC drivers
still checked for nullified domains.  Remove the obsolete checks.

Fixes: c8d87704 ("pmdomain: renesas: rcar-sysc: Remove rcar_sysc_nullify() helper")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/107f2bf9f13b29f0f623d2959a5347ec151fb089.1745840768.git.geert+renesas@glider.be


Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>