Modify the file main.cpp for M487

Dependencies:   BufferedSerial

Revision:
0:c89ccc69a48b
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/NuMaker-mbed-SD-driver.lib	Fri Sep 29 05:45:43 2017 +0000
@@ -0,0 +1,1 @@
+https://github.com/OpenNuvoton/NuMaker-mbed-SD-driver/#253f370c308331fc9a82b5387ed108750ac70ac8