Fix explicit specialization in non-namespace scope

Fixes #2614

Author: ferdymercury

include/oneapi/dpl/internal/random_impl/extreme_value_distribution.h

@@ -210,14 +210,10 @@ class extreme_value_distribution
     inline scalar_type
     callback()
     {
-        return ((scalar_type*)(internal::gaussian_sp_table))[1];
-    }
-
-    template <>
-    inline scalar_type
-    callback<double>()
-    {
-        return ((scalar_type*)(internal::gaussian_dp_table))[1];
+        if constexpr (std::is_same_v<_Type, double>)
+            return ((scalar_type*)(internal::gaussian_dp_table))[1];
+        else
+            return ((scalar_type*)(internal::gaussian_sp_table))[1];
     }
 
     // Implementation for generate function

include/oneapi/dpl/internal/random_impl/normal_distribution.h

@@ -262,29 +262,21 @@ class normal_distribution
     inline scalar_type
     callback()
     {
-        return ((scalar_type*)(internal::gaussian_sp_table))[1];
-    }
-
-    template <>
-    inline scalar_type
-    callback<double>()
-    {
-        return ((scalar_type*)(internal::gaussian_dp_table))[1];
+        if constexpr (std::is_same_v<_Type, double>)
+            return ((scalar_type*)(internal::gaussian_dp_table))[1];
+        else
+            return ((scalar_type*)(internal::gaussian_sp_table))[1];
     }
 
     // Get 2 * pi function
     template <typename _Type = float>
     inline scalar_type
     pi2()
     {
-        return ((scalar_type*)(internal::gaussian_sp_table))[0];
-    }
-
-    template <>
-    inline scalar_type
-    pi2<double>()
-    {
-        return ((scalar_type*)(internal::gaussian_dp_table))[0];
+        if constexpr (std::is_same_v<_Type, double>)
+            return ((scalar_type*)(internal::gaussian_dp_table))[0];
+        else
+            return ((scalar_type*)(internal::gaussian_sp_table))[0];
     }
 
     // Implementation for generate function