irqchip/dw-apb-ictl: Fix generic domain chip wreckage

The num_ct argument of irq_alloc_domain_generic_chips() tells the core
code how many chip types (for different control flows,
e.g. edge/level) should be allocated. It does not control how many
generic chip instances are created because that's determined from the
irq domain size and the number of interrupts per chip.

The dw-apb init abuses the num_ct argument for allocating one or two
chip types depending on the number of interrupts. That's completely
wrong because the alternate type is never used.

This code was obviously never tested on a system which has more than
32 interrupts as that would have never worked due to the unitialized
second generic chip instance.

Hand in the proper num_ct=1 and fixup the chip initialization along
with the interrupt handler.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Jisheng Zhang <jszhang@marvell.com>
Cc: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Jason Cooper <jason@lakedaemon.net>
Link: http://lkml.kernel.org/r/20150706101543.373582262@linutronix.de