mfd: Fix generic irq chip ack function name for jz4740-adc

In commit 659fb32d("genirq: replace irq_gc_ack() with {set,clr}_bit
variants"), irq_gc_ack was renamed to irq_gc_ack_set_bit. The jz4740-adc
driver still uses the old name which results in a compile error.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

drivers/mfd/jz4740-adc.c

@@ -273,7 +273,7 @@ static int __devinit jz4740_adc_probe(struct platform_device *pdev)
 	ct->regs.ack = JZ_REG_ADC_STATUS;
 	ct->chip.irq_mask = irq_gc_mask_set_bit;
 	ct->chip.irq_unmask = irq_gc_mask_clr_bit;
-	ct->chip.irq_ack = irq_gc_ack;
+	ct->chip.irq_ack = irq_gc_ack_set_bit;
 
 	irq_setup_generic_chip(gc, IRQ_MSK(5), 0, 0, IRQ_NOPROBE | IRQ_LEVEL);