pinctrl: renesas: Remove sh_pfc_config_mux_for_gpio()

pinctrl: renesas: Remove sh_pfc_config_mux_for_gpio()

This function is now replaced by common pin controller GPIO configuration
functionality, drop it.

Signed-off-by: Marek Vasut <[email protected]>
Cc: Alex Kiernan <[email protected]>
Cc: Christoph Muellner <[email protected]>
Cc: Eugeniu Rosca <[email protected]>
Cc: Patrice Chotard <[email protected]>
Cc: Patrick DELAUNAY <[email protected]>
Cc: Philipp Tomsich <[email protected]>
Cc: Simon Glass <[email protected]>