gpio: eic: sprd: Fix the incorrect EIC offset when toggling

commit e91aafcb51f3c5001ae76c3ee027beb0b8506447 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>