drm/i915: move wedged to the other gpu error handling stuff

And to make Ben Widawsky happier, use the gpu_error instead of
the entire device as the argument in some functions.

Drop the outdated comment on ->wedged for now, a follow-up patch will
change the semantics and add a proper comment again.

Reviewed-by: Damien Lespiau <damien.lespiau@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_debugfs.c

@@ -1672,7 +1672,7 @@ i915_wedged_read(struct file *filp,
 
 	len = snprintf(buf, sizeof(buf),
 		       "wedged :  %d\n",
-		       atomic_read(&dev_priv->mm.wedged));
+		       atomic_read(&dev_priv->gpu_error.wedged));
 
 	if (len > sizeof(buf))
 		len = sizeof(buf);