omap: gpmc-smsc911x: always set irq flags to IORESOURCE_IRQ_LOWLEVEL

SMSC911x devices attached to OMAP GPMC always use low level irqs.
Setting the appropriate flag in the irq resourse strucure allows using
.flags field in the omap_smsc911x_platform_data for driver specific
flags

Signed-off-by: Mike Rapoport <mike@compulab.co.il>
Signed-off-by: Tony Lindgren <tony@atomide.com>