pinctrl: renesas: rzg2l: Add function pointers for OEN register access

pinctrl: renesas: rzg2l: Add function pointers for OEN register access

Introduce function pointers oen_read() and oen_write(), in the struct
rzg2l_pinctrl_data to facilitate reading and writing to the PFC_OEN
register.  On the RZ/V2H(P) SoC, unlocking the PWPR.REGWE_B bit before
writing to the PFC_OEN register is necessary, and the PFC_OEN register
has more bits compared to the RZ/G2L family.  To handle these
differences between RZ/G2L and RZ/V2H(P) and to reuse the existing code
for RZ/V2H(P), these function pointers are introduced.

Additionally, populate these function pointers with appropriate data for
existing SoCs.

Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Tested-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com> # on RZ/G3S
Link: https://lore.kernel.org/r/20240530173857.164073-10-prabhakar.mahadev-lad.rj@bp.renesas.com
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>