pinctrl: renesas: Add PORT_GP_CFG_13 macros

Add PORT_GP_CFG_13() and PORT_GP_13() helper macros, to be used by the
r8a779g0 subdriver.

Based on a larger patch in the BSP by LUU HOAI.

Signed-off-by: LUU HOAI <hoai.luu.ub@renesas.com>
Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Link: https://lore.kernel.org/r/87edz5ty0r.wl-kuninori.morimoto.gx@renesas.com


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