Fix a typo.

Change-Id: I3c8ab03932d8769c1cf0c0ccf84cd150c5eb82d8
Signed-off-by: John Szakmeister <john@szakmeister.net>
Reviewed-on: http://openocd.zylin.com/1481
Reviewed-by: Xiaofan <xiaofanc@gmail.com>
Tested-by: jenkins
Reviewed-by: Andreas Fritiofson <andreas.fritiofson@gmail.com>