mmc: omap_hsmmc: pass IRQF_ONESHOT to request_threaded_irq

The flag of IRQF_ONESHOT should be passed to request_threaded_irq,
otherwise the following failure message should be dumped because
hardware handler is defined as NULL:

[    3.383483] genirq: Threaded irq requested with handler=NULL and
!ONESHOT for irq 368
[    3.392730] omap_hsmmc: probe of omap_hsmmc.0 failed with error -22

The patch fixes one kernel hang bug which is caused by mmc card
probe failure and root device can't be brought up.

Signed-off-by: Ming Lei <ming.lei@canonical.com>
Acked-by: Venkatraman S <svenkatr@ti.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Chris Ball <cjb@laptop.org>