gpio: mpc8xxx: Fixup setting gpio direction output

For devtype with specific gpio_dir_out implementation, current code is
wrong because below code sets both gc->direction_output and
mpc8xxx_gc->direction_output to the same function.

gc->direction_output = devtype->gpio_dir_out ?: gc->direction_output;
mpc8xxx_gc->direction_output = gc->direction_output;

Set mpc8xxx_gc->direction_output = gc->direction_output first to fix it.
This way mpc8xxx_gc->direction_output actually calls the standard
bgpio_dir_out() to update register.

Fixes: commit 42178e2a ("drivers/gpio: Switch gpio-mpc8xxx to use gpio-generic")
Signed-off-by: Axel Lin <axel.lin@ingics.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>