drm/i915: Remove superfluous wait_for_error() from throttle-ioctl

The throttle-ioctl never touches the struct_mutex. It does, however, as
part of its ABI report whether the hardware is terminally wedged. For
that purposes, it only has to report the current state and not incur the
cost of checking/waiting every invocation, as we do not have to wait for
a reset before waiting on a request to ensure completion (that is baked
into the wait request implementation).
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20161028125858.23563-3-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/i915_gem.c

@@ -3705,10 +3705,6 @@ i915_gem_ring_throttle(struct drm_device *dev, struct drm_file *file)
 	struct drm_i915_gem_request *request, *target = NULL;
 	int ret;
 
-	ret = i915_gem_wait_for_error(&dev_priv->gpu_error);
-	if (ret)
-		return ret;
-
 	/* ABI: return -EIO if already wedged */
 	if (i915_terminally_wedged(&dev_priv->gpu_error))
 		return -EIO;