drm/i915: Downgrade incorrect engine constructor usage warnings to development

Render engine constructor helpers must only be called from the render
engine constructors, but there is no need to burden the production
binaries with warnings which can only be triggered during development.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Michel Thierry <michel.thierry@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Michel Thierry <michel.thierry@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180119100005.9072-1-tvrtko.ursulin@linux.intel.com

drivers/gpu/drm/i915/intel_engine_cs.c

@@ -1394,7 +1394,8 @@ int init_workarounds_ring(struct intel_engine_cs *engine)
 	struct drm_i915_private *dev_priv = engine->i915;
 	int err;
 
-	WARN_ON(engine->id != RCS);
+	if (GEM_WARN_ON(engine->id != RCS))
+		return -EINVAL;
 
 	dev_priv->workarounds.count = 0;
 	dev_priv->workarounds.hw_whitelist_count[engine->id] = 0;

drivers/gpu/drm/i915/intel_lrc.c

@@ -1414,7 +1414,7 @@ static int intel_init_workaround_bb(struct intel_engine_cs *engine)
 	unsigned int i;
 	int ret;
 
-	if (WARN_ON(engine->id != RCS || !engine->scratch))
+	if (GEM_WARN_ON(engine->id != RCS || !engine->scratch))
 		return -EINVAL;
 
 	switch (INTEL_GEN(engine->i915)) {