pinctrl: exynos: ack level-triggered interrupts before unmasking

A level-triggered interrupt should be acked after the interrupt line
becomes inactive and before it is unmasked, or else another interrupt
will be immediately triggered.  Acking before or after calling the
handler is not enough.

Signed-off-by: Luigi Semenzato <semenzato@chromium.org>
Signed-off-by: Doug Anderson <dianders@chromium.org>
Acked-by: Tomasz Figa <t.figa@samsung.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>