pinctrl: intel: Clear interrupt status in mask/unmask callback

Commit a939bb57

 ("pinctrl: intel: implement gpio_irq_enable") was
added because clearing interrupt status bit is required to avoid
unexpected behavior.

Turns out the unmask callback also needs the fix, which can solve weird
IRQ triggering issues on I2C touchpad ELAN1200.

Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>