When toggling the level trigger to emulate the edge trigger, the
EIC offset is incorrect without adding the corresponding bank index,
thus fix it.

Fixes: 7bf0d7f6 ("gpio: eic: Add edge trigger emulation for EIC")
Cc: stable@vger.kernel.org
Signed-off-by: Bruce Chen <bruce.chen@unisoc.com>
Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>