[SYCL][NFC] Add missed '#pragma once' (#984)

Signed-off-by: Alexey Sachkov <[email protected]>

Author: AlexeySachkov

sycl/include/CL/sycl/detail/generic_type_lists.hpp

@@ -6,6 +6,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+#pragma once
+
 #include <CL/sycl/access/access.hpp>
 #include <CL/sycl/detail/stl_type_traits.hpp>
 #include <CL/sycl/detail/type_list.hpp>

sycl/include/CL/sycl/detail/image_accessor_util.hpp

@@ -8,6 +8,9 @@
 // This file includes some utilities that are used by image accessors on host
 // device
 //
+
+#pragma once
+
 #ifndef __SYCL_DEVICE_ONLY__
 #include <CL/sycl/builtins.hpp>
 #include <CL/sycl/detail/generic_type_traits.hpp>