sh-pfc: Don't modify sh_pfc_pin SoC data

The sh_pfc_pin structure supplied in SoC data contains information about
pin configuration and name. It's abused to store GPIO data registers
information and pin config type. Move those fields out of the
pinmux_data_reg structure into the new sh_pfc_gpio_pin and
sh_pfc_pin_config structures.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>