gpio: Add RZ/G2L GPIO driver

This driver adds support for the gpio features of the GPIO/PFC module in
the Renesas RZ/G2L (R9A07G044) SoC.

The new `rzg2l-pfc-gpio` driver is bound to the same device tree node as
the `rzg2l-pfc-pinctrl` driver as the same hardware block provides both
GPIO and pin multiplexing features.

This patch is based on the corresponding Linux v6.5 driver
(commit 52e12027d50affbf60c6c9c64db8017391b0c22e).

Signed-off-by: Paul Barker <paul.barker.ct@bp.renesas.com>
Reviewed-by: Biju Das <biju.das.jz@bp.renesas.com>
Reviewed-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Marek Vasut <marek.vasut+renesas@mailbox.org>