drm/i915: check i915_get_reset_stats_ioctl args

Insist that flags and pad fields are zero, so that
we can safely extend the interface in future.

Testcase: igt/gem_reset_stats/params
Suggested-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: NMika Kuoppala <mika.kuoppala@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_uncore.c

@@ -641,6 +641,9 @@ int i915_get_reset_stats_ioctl(struct drm_device *dev,
 	struct i915_ctx_hang_stats *hs;
 	int ret;
 
+	if (args->flags || args->pad)
+		return -EINVAL;
+
 	if (args->ctx_id == DEFAULT_CONTEXT_ID && !capable(CAP_SYS_ADMIN))
 		return -EPERM;