pinctrl: renesas: rzg2l: Clarify OEN read/write support

pinctrl: renesas: rzg2l: Clarify OEN read/write support

We currently support OEN read/write for the RZ/G3S SoC but not the
RZ/G2L SoC family (consisting of RZ/G2L, RZ/G2LC, RZ/G2UL, RZ/V2L &
RZ/Five). The appropriate functions are renamed to clarify this and to
match the callback names.

We should also only set the oen_read and oen_write function pointers for
the devices which support these operations. This requires us to check
that these function pointers are valid before calling them.

Signed-off-by: Paul Barker <paul.barker.ct@bp.renesas.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/20240625200316.4282-2-paul.barker.ct@bp.renesas.com
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>