omap: iommu: Return IRQ_HANDLED in fault handler when no fault occured

Commit d594f1f3 (omap: IOMMU: add
support to callback during fault handling) broke interrupt line sharing
between the OMAP3 ISP and its IOMMU. Because of this, every interrupt
generated by the OMAP3 ISP is handled by the IOMMU driver instead of
being passed to the OMAP3 ISP driver.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Hiroshi DOYU <Hiroshi.DOYU@nokia.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>