drm/i915: Remove one very outdated comment

Comment disagrees with the code which has changed a lot since
it was documented.

Note that the logic to remove -EIO handling was dropped in

commit 1488fc08
Author: Chris Wilson <chris@chris-wilson.co.uk>
Date:   Tue Apr 24 15:47:31 2012 +0100

    drm/i915: Remove the deferred-free list
Signed-off-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_gem.c

@@ -3230,10 +3230,6 @@ int i915_vma_unbind(struct i915_vma *vma)
 	ret = i915_gem_object_wait_rendering(obj, false);
 	if (ret)
 		return ret;
-	/* Continue on if we fail due to EIO, the GPU is hung so we
-	 * should be safe and we need to cleanup or else we might
-	 * cause memory corruption through use-after-free.
-	 */
 
 	if (i915_is_ggtt(vma->vm) &&
 	    vma->ggtt_view.type == I915_GGTT_VIEW_NORMAL) {