drm/i915: Fix retrieval of hangcheck stats

The default context is always supported (as it contains the global
hangcheck stats) and the contexts for hangcheck are not limited
to any ring.

This was dropped in 2013 because it was supposed to have been included
with Ben's full-ppgtt patch set. It never landed and the bug remains.

References: https://bugs.freedesktop.org/show_bug.cgi?id=65845
Link: http://patchwork.freedesktop.org/patch/msgid/[email protected]
Signed-off-by: Chris Wilson <[email protected]>
Reviewed-by: Mika Kuoppala <[email protected]>
Link: http://patchwork.freedesktop.org/patch/msgid/[email protected]

Author: ickle

drivers/gpu/drm/i915/i915_gem_context.c

@@ -1034,9 +1034,6 @@ int i915_gem_context_reset_stats_ioctl(struct drm_device *dev,
 	if (args->flags || args->pad)
 		return -EINVAL;
 
-	if (args->ctx_id == DEFAULT_CONTEXT_HANDLE && !capable(CAP_SYS_ADMIN))
-		return -EPERM;
-
 	ret = i915_mutex_lock_interruptible(dev);
 	if (ret)
 		return ret;