i915: return -EFAULT if copy_to_user fails

copy_to_user() returns the number of bytes remaining to be copied and
I'm pretty sure we want to return a negative error code here.
Signed-off-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: stable@kernel.org

drivers/gpu/drm/i915/i915_gem.c

@@ -3588,6 +3588,7 @@ i915_gem_do_execbuffer(struct drm_device *dev, void *data,
 		if (ret != 0) {
 			DRM_ERROR("copy %d cliprects failed: %d\n",
 				  args->num_cliprects, ret);
+			ret = -EFAULT;
 			goto pre_mutex_err;
 		}
 	}