pinctrl: renesas: rzt2h: Skip PFC mode configuration if already set

pinctrl: renesas: rzt2h: Skip PFC mode configuration if already set

In rzt2h_pinctrl_set_pfc_mode(), read the PMC and PFC registers upfront
and skip the pin function configuration if the pin is already in
peripheral mode with the desired function.

Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://patch.msgid.link/20260513115312.1574367-3-prabhakar.mahadev-lad.rj@bp.renesas.com
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>