Correct USART init for stm32 autobauding

Hello,

I had some headache trying to figure out the issue when flashing some stm32 mcu over uart [1] 

With the above changes i can now flash stm32 devices correctly.

regards,

1 : http://www.st.com/web/en/resource/technical/document/application_note/CD00264342.pdf
source formating :replaced tab
Merge pull request #82 from treymarc/patch-1

Correct USART init for stm32 autobauding