drm/i915: don't try to load GuC fw on pre-gen9

This avoids some bad register writes and generally feels more correct
than unconditionally trying to redirect interrupts and such.

References: https://bugs.freedesktop.org/show_bug.cgi?id=91777
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_gem.c

@@ -4687,6 +4687,7 @@ i915_gem_init_hw(struct drm_device *dev)
 	}
 
 	/* We can't enable contexts until all firmware is loaded */
+	if (HAS_GUC_UCODE(dev)) {
 		ret = intel_guc_ucode_load(dev);
 		if (ret) {
 			/*
@@ -4696,11 +4697,13 @@ i915_gem_init_hw(struct drm_device *dev)
 			 * discard the error and carry on.
 			 */
 			DRM_ERROR("Failed to initialize GuC, error %d%s\n", ret,
-			i915.enable_guc_submission ? "" : " (ignored)");
+				  i915.enable_guc_submission ? "" :
+				  " (ignored)");
 			ret = i915.enable_guc_submission ? -EIO : 0;
 			if (ret)
 				goto out;
 		}
+	}
 
 	/* Now it is safe to go back round and do everything else: */
 	for_each_ring(ring, dev_priv, i) {