ARM: S3C64XX: Fix WM8915 IRQ polarity on Cragganmore

The chip IRQ output is genuinely an IRQ output rather than /IRQ output by
default - this had been working due to an interface issue with the IRQ
controller.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>