pinctrl: sh-pfc: Add new flags into struct sh_pfc_pin_config

To clean/modify the code up later, this patch just adds new flags
"mux_set" and "gpio_enabled" into the struct sh_pfc_pin_config.

Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>