include/mem_layout_common.h: add "C" header guard for C++ compatibility

include/mem_layout_common.h

 #ifndef _MEM_LAYOUT_COMMON_
 #define _MEM_LAYOUT_COMMON_
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 #include "pcie_regs.h"
 
 /* FMC_ACTIVE_CLK Component */
@@ -82,4 +86,8 @@
 /* Large Memory Addresses */
 #define LARGE_MEM_ADDR                              (BAR2_ADDR | LARGE_MEM_RAW_ADDR)
 
+#ifdef __cplusplus
+}
+#endif
+
 #endif