MAINTAINERS: Generalize ARM/RISC-V/RENESAS ARCHITECTURE

Triggered by noticing that the pwm-rcar driver isn't covered by the
Renesas maintainer entry, add this driver to it. Instead of adding it
explicitly, just add a file regex for "rcar" (and drop the one entry
that gets redundant by that).

Looking at the output of

	$ git ls-files | grep rcar

only shows files related to that architecture, so no X: line is
currently needed.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@baylibre.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/20250404080045.367845-2-u.kleine-koenig@baylibre.com


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