gpio: mpc8xxx: ls1088a/ls1028a edge detection mode bug fixs.

On these boards, the irq_set_type must point one valid function pointer
that can correctly set both edge and falling edge.
Signed-off-by: Song Hui <hui.song_1@nxp.com>
Link: https://lore.kernel.org/r/20191122061839.24904-1-hui.song_1@nxp.comSigned-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/gpio/gpio-mpc8xxx.c

@@ -296,6 +296,7 @@ static const struct mpc8xxx_gpio_devtype mpc512x_gpio_devtype = {
 
 static const struct mpc8xxx_gpio_devtype ls1028a_gpio_devtype = {
 	.gpio_dir_in_init = ls1028a_gpio_dir_in_init,
+	.irq_set_type = mpc8xxx_irq_set_type,
 };
 
 static const struct mpc8xxx_gpio_devtype mpc5125_gpio_devtype = {