add -n parameter to stmloader to prevent sending reboot sequence in case STM32 was already in bootloader mode (by fiendie)

git-svn-id: https://afrodevices.googlecode.com/svn/trunk/baseflight@266 7c89a4a9-59b9-e629-4cfe-3a2d53b20e61
Merge https://github.com/cGiesen/baseflight