Fixed texture side iterator being too small (#3026)

src/renderer_d3d12.cpp

@@ -5099,7 +5099,7 @@ namespace bgfx { namespace d3d12
 				, swizzle ? " (swizzle BGRA8 -> RGBA8)" : ""
 				);
 
-			for (uint8_t side = 0; side < numSides; ++side)
+			for (uint16_t side = 0; side < numSides; ++side)
 			{
 				for (uint8_t lod = 0; lod < ti.numMips; ++lod)
 				{