libfdt: add extern "C" for C++

Signed-off-by: Patrick Oppenlander <patrick.oppenlander@gmail.com>
Message-Id: <20200616011217.15253-1-patrick.oppenlander@gmail.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

libfdt/libfdt.h

@@ -9,6 +9,10 @@
 #include <libfdt_env.h>
 #include <fdt.h>
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 #define FDT_FIRST_SUPPORTED_VERSION	0x02
 #define FDT_LAST_SUPPORTED_VERSION	0x11
 
@@ -2069,4 +2073,8 @@ int fdt_overlay_apply(void *fdt, void *fdto);
 
 const char *fdt_strerror(int errval);
 
+#ifdef __cplusplus
+}
+#endif
+
 #endif /* LIBFDT_H */