drm/i915/selftests: Skip huge pages live tests if wedged

We test the GPU handling of huge pages by submitting requests that write
into a huge page, but if the GPU is irrecoverably wedged we cannot
submit any requests. As the test expectedly fails, skip over it.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180706065332.15214-8-chris@chris-wilson.co.uk