add missing includes to rich_comparisons

Author: ndgrigorian

dpctl/tensor/libtensor/include/utils/rich_comparisons.hpp

@@ -24,9 +24,12 @@
 
 #pragma once
 
-#include "sycl/sycl.hpp"
+#include <cmath>
+#include <complex>
 #include <type_traits>
 
+#include "sycl/sycl.hpp"
+
 namespace dpctl
 {
 namespace tensor