iio: twl4030-madc: Pass the IRQF_ONESHOT flag

Since commit 1c6c6952 ("genirq: Reject bogus threaded irq requests")
threaded IRQs without a primary handler need to be requested with
IRQF_ONESHOT, otherwise the request will fail.

So pass the IRQF_ONESHOT flag in this case.

The semantic patch that makes this change is available
in scripts/coccinelle/misc/irqf_oneshot.cocci.

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>