drivers/mfd: remove obsolete irq_desc_t typedef

The defines and typedefs (hw_interrupt_type, no_irq_type, irq_desc_t) have
been kept around for migration reasons.  After more than two years it's
time to remove them finally.

This patch cleans up one of the remaining users.  When all such patches
hit mainline we can remove the defines and typedefs finally.

Impact: cleanup

Convert the last remaining users and remove the typedef.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

drivers/mfd/twl4030-irq.c

@@ -255,7 +255,7 @@ static int twl4030_irq_thread(void *data)
  * thread.  All we do here is acknowledge and mask the interrupt and wakeup
  * the kernel thread.
  */
-static void handle_twl4030_pih(unsigned int irq, irq_desc_t *desc)
+static void handle_twl4030_pih(unsigned int irq, struct irq_desc *desc)
 {
 	/* Acknowledge, clear *AND* mask the interrupt... */
 	desc->chip->ack(irq);