add exist git repo up to github

Take uboot_savage_mx6 as example.

1. git remote add pb https://github.com/allencyhsu/uboot_savage_mx6.git

2. git remote -v

origin  git://git.freescale.com/imx/uboot-imx.git (fetch)

origin  git://git.freescale.com/imx/uboot-imx.git (push)

pb  https://github.com/allencyhsu/uboot_savage_mx6.git (fetch)

pb  https://github.com/allencyhsu/uboot_savage_mx6.git (push)

3. git push pb savage-jb

   answer the id & pass question.

4. wait couple minutes to complete upload.

5. go to github to check the code uploaded.