pinctrl: microchip-sgpio: Fix wrong register offset for IRQ trigger

pinctrl: microchip-sgpio: Fix wrong register offset for IRQ trigger

This patch fixes using a wrong register offset when configuring an IRQ
trigger type.

Fixes: be2dc859abd4 ("pinctrl: pinctrl-microchip-sgpio: Add irq support (for sparx5)")
Reported-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Lars Povlsen <lars.povlsen@microchip.com>
Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Link: https://lore.kernel.org/r/20210203123825.611576-1-lars.povlsen@microchip.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>