drm/omap: EBUSY status handling in omap_gem_fault()

Subsequent threads returning EBUSY from vm_insert_pfn() was not
handled correctly. As a result concurrent access from new threads
to mmapped data caused SIGBUS.

See e79e0fe3 ("drm/i915: EBUSY status
handling added to i915_gem_fault()").

Signed-off-by: Rob Clark <robdclark@gmail.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>