pinctrl: sh-pfc: Kill unused variable in sh_pfc_remove()

If CONFIG_PINCTRL_SH_PFC_GPIO=n:

    drivers/pinctrl/sh-pfc/core.c: In function 'sh_pfc_remove':
    drivers/pinctrl/sh-pfc/core.c:649:17: warning: unused variable 'pfc' [-Wunused-variable]

Fixes: 67ec8d7b

 ("pinctrl: ish-pfc: Use devm_pinctrl_register() for pinctrl registration")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>