drm/i915: Bug on unsupported swizzled platforms

Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_gem.c

@@ -3897,8 +3897,10 @@ void i915_gem_init_swizzling(struct drm_device *dev)
 	I915_WRITE(TILECTL, I915_READ(TILECTL) | TILECTL_SWZCTL);
 	if (IS_GEN6(dev))
 		I915_WRITE(ARB_MODE, _MASKED_BIT_ENABLE(ARB_MODE_SWIZZLE_SNB));
-	else
+	else if (IS_GEN7(dev))
 		I915_WRITE(ARB_MODE, _MASKED_BIT_ENABLE(ARB_MODE_SWIZZLE_IVB));
+	else
+		BUG();
 }
 
 static bool