f2fs-tools: change SRC_URI to use git repo on kernel.org

* sf does not provide tarballs anymore:
  The f2fs-tools is no longer maintained through sf.net.
  Instead, please access the following url.
  http://git.kernel.org/?p=linux/kernel/git/jaegeuk/f2fs-tools.git;a=summary



Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>