mfd: Convert WM835x to new irq_ interrupt methods

Kernel 2.6.37 adds new interrupt methods which take a struct irq_data
rather than an irq number. Convert over to these as they will become
mandatory in future.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>