pinctrl: sh-pfc: Unlock on error in sh_pfc_func_set_mux()

We need to unlock and enable IRQs before we return on this error path.

Fixes: 8a0cc47c ("pinctrl: sh-pfc: Rollback to mux if required when the gpio is freed")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Link: https://lore.kernel.org/r/20190827093927.GB8443@mwanda


Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>