Use sycl::ext::oneapi::experimental::pow in pow.hpp for complexes in-place

Author: oleksandr-pavlyk

dpctl/tensor/libtensor/include/kernels/elementwise_functions/pow.hpp

@@ -361,11 +361,20 @@ template <typename argT, typename resT> struct PowInplaceFunctor
                 tmp1 *= tmp1;
             }
             res = res_tmp;
-            return;
+        }
+        else if constexpr (tu_ns::is_complex<argT>::value &&
+                           tu_ns::is_complex<resT>::value)
+        {
+            using r_resT = typename resT::value_type;
+            using r_argT = typename argT::value_type;
+
+            res = exprm_ns::pow(exprm_ns::complex<r_resT>(res),
+                                exprm_ns::complex<r_argT>(in));
         }
         else {
             res = std::pow(res, in);
-        };
+        }
+        return;
     }
 
     template <int vec_sz>