gpio: sprd: Remove unused irq trigger setting

The Spreadtrum PMIC interrupt controller has no registers to set irq
trigger type, since it is always high level trigger. That means the
PMIC EIC controller as a child device of PMIC INTC does not need to
set the trigger type, so remove it.

Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>