Cycles: SSE optimization for Voronoi cells texture

Gives 5-6% speedup for Caterpillar_PatazStudio.blend.

Reviewed By: brecht, dingto

Differential Revision: https://developer.blender.org/D419

intern/cycles/util/util_math.h

@@ -163,11 +163,7 @@ ccl_device_inline float clamp(float a, float mn, float mx)
 
 ccl_device_inline int float_to_int(float f)
 {
-#if defined(__KERNEL_SSE2__) && !defined(_MSC_VER)
-	return _mm_cvtt_ss2si(_mm_load_ss(&f));
-#else
 	return (int)f;
-#endif
 }
 
 ccl_device_inline int floor_to_int(float f)