mfd: Fix asic3 build error

Fix below compile error:

  CC      drivers/mfd/asic3.o
drivers/mfd/asic3.c: In function 'asic3_irq_demux':
drivers/mfd/asic3.c:147: error: 'irq_data' undeclared (first use in this function)
drivers/mfd/asic3.c:147: error: (Each undeclared identifier is reported only once
drivers/mfd/asic3.c:147: error: for each function it appears in.)

Signed-off-by: Axel Lin <axel.lin@gmail.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>