Add missing pragma once to the header files

Author: antonwolfy

dpnp/backend/extensions/common/ext/details/common_internal.hpp

@@ -26,6 +26,8 @@
 // THE POSSIBILITY OF SUCH DAMAGE.
 //*****************************************************************************
 
+#pragma once
+
 #include <algorithm>
 
 #include "ext/common.hpp"

dpnp/backend/extensions/common/ext/details/validation_utils_internal.hpp

@@ -26,6 +26,8 @@
 // THE POSSIBILITY OF SUCH DAMAGE.
 //*****************************************************************************
 
+#pragma once
+
 #include <pybind11/numpy.h>
 #include <pybind11/pybind11.h>