Add extern "C" to headers

Add extern "C" to headers so that they can be included by cpp code.

Signed-off-by: Deepak Kodihalli <dkodihal@in.ibm.com>
diff --git a/libmctp-serial.h b/libmctp-serial.h
index 0d3b972..68f184e 100644
--- a/libmctp-serial.h
+++ b/libmctp-serial.h
@@ -3,6 +3,10 @@
 #ifndef _LIBMCTP_SERIAL_H
 #define _LIBMCTP_SERIAL_H
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 #include "libmctp.h"
 
 struct mctp_binding_serial;
@@ -16,4 +20,8 @@
 		const char *path);
 void mctp_serial_open_fd(struct mctp_binding_serial *serial, int fd);
 
+#ifdef __cplusplus
+}
+#endif
+
 #endif /* _LIBMCTP_SERIAL_H */