Cycles: Add some sanity check asserts in the traversal code

This way we'll be sure (in debug builds) that regular BVH traversal is not used
for QBVH tree (could happen because of mismatch of logic in kernel and render).

intern/cycles/kernel/geom/geom_bvh_shadow.h

@@ -394,6 +394,7 @@ ccl_device_inline bool BVH_FUNCTION_NAME(KernelGlobals *kg,
 	else
 #endif
 	{
+		kernel_assert(kernel_data.bvh.use_qbvh == false);
 		return BVH_FUNCTION_FULL_NAME(BVH)(kg,
 		                                   ray,
 		                                   isect_array,

intern/cycles/kernel/geom/geom_bvh_subsurface.h

@@ -316,6 +316,7 @@ ccl_device_inline uint BVH_FUNCTION_NAME(KernelGlobals *kg,
 	else
 #endif
 	{
+		kernel_assert(kernel_data.bvh.use_qbvh == false);
 		return BVH_FUNCTION_FULL_NAME(BVH)(kg,
 		                                   ray,
 		                                   isect_array,

intern/cycles/kernel/geom/geom_bvh_traversal.h

@@ -401,6 +401,7 @@ ccl_device_inline bool BVH_FUNCTION_NAME(KernelGlobals *kg,
 	else
 #endif
 	{
+		kernel_assert(kernel_data.bvh.use_qbvh == false);
 		return BVH_FUNCTION_FULL_NAME(BVH)(kg,
 		                                   ray,
 		                                   isect,

intern/cycles/kernel/geom/geom_bvh_volume.h

@@ -327,6 +327,7 @@ ccl_device_inline bool BVH_FUNCTION_NAME(KernelGlobals *kg,
 	else
 #endif
 	{
+		kernel_assert(kernel_data.bvh.use_qbvh == false);
 		return BVH_FUNCTION_FULL_NAME(BVH)(kg,
 		                                   ray,
 		                                   isect);