drm/i915: Refresh the errno to vmf_fault translations

It's been a long time since we accidentally reported -EIO upon wedging,
it can now only be generated by failure to swap in a page.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Abdiel Janulgue <abdiel.janulgue@linux.intel.com>
Reviewed-by: Abdiel Janulgue <abdiel.janulgue@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190902040303.14195-4-chris@chris-wilson.co.uk