ARM: OMAP2+: remove incorrect irq_chip ack field

Each irq_chip for the main interrupt controller has offsets set for irq
masking registers, which added to respective base results in a pointer
to appropriate hardware register. However this is not correct for
INTC_CONTROL as there is only one INTC_CONTROL register. This does not
cause problems because generic ack code is never called, but remove
this assignment to avoid confusion.
Signed-off-by: Grazvydas Ignotas <notasas@gmail.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>

arch/arm/mach-omap2/irq.c

@@ -149,7 +149,6 @@ omap_alloc_gc(void __iomem *base, unsigned int irq_start, unsigned int num)
 	ct->chip.irq_mask = irq_gc_mask_disable_reg;
 	ct->chip.irq_unmask = irq_gc_unmask_enable_reg;
 
-	ct->regs.ack = INTC_CONTROL;
 	ct->regs.enable = INTC_MIR_CLEAR0;
 	ct->regs.disable = INTC_MIR_SET0;
 	irq_setup_generic_chip(gc, IRQ_MSK(num), IRQ_GC_INIT_MASK_CACHE,