iio: exynos-adc: fix irqf_oneshot.cocci warnings

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.

Generated by: scripts/coccinelle/misc/irqf_oneshot.cocci

Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Valentin Rothberg <valentinrothberg@gmail.com>
Signed-off-by: Olof Johansson <olof@lixom.net>