Currently R-Car M3-W and M3-W+ are handled by a single sub-driver,
but using separate Kconfig symbols and separate rcar_sysc_info
structures, and fixup code to handle the remaining differences.

Prepare for handling more differences by splitting them in two separate
sub-drivers.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Link: https://lore.kernel.org/r/a416e2bae7227c08d7e7d158366ab021f4d6cc18.1713348705.git.geert+renesas@glider.beSigned-off-by: Ulf Hansson <ulf.hansson@linaro.org>