mfd: jz4740-adc: Init mask cache in generic IRQ chip

The mask cache must be initialised in the generic IRQ chip,
otherwise enabling one channel will actually enable all
channels when the empty mask cache is written.

Signed-off-by: Matt Redfearn <matt.redfearn@imgtec.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
diff --git a/drivers/mfd/jz4740-adc.c b/drivers/mfd/jz4740-adc.c
index 408291c..5bb49f0 100644
--- a/drivers/mfd/jz4740-adc.c
+++ b/drivers/mfd/jz4740-adc.c
@@ -273,7 +273,8 @@
 	ct->chip.irq_unmask = irq_gc_mask_clr_bit;
 	ct->chip.irq_ack = irq_gc_ack_set_bit;
 
-	irq_setup_generic_chip(gc, IRQ_MSK(5), 0, 0, IRQ_NOPROBE | IRQ_LEVEL);
+	irq_setup_generic_chip(gc, IRQ_MSK(5), IRQ_GC_INIT_MASK_CACHE, 0,
+				IRQ_NOPROBE | IRQ_LEVEL);
 
 	adc->gc = gc;