mfd: Make sure to request twl6030 IRQ before using the irq_num

I was trying to fix the error handling part because in the case of
request_irq failure, it should call kthread_stop instead of free_irq.
But it seems more reasonable to do request_irq before calling kthread_run.

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