git.kernel.org isn't down, it just looks like they've changed the directory structure. Try the following git command in place of the one in the Freescale instructions:
git clone git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git kernel_imx
This will get you a more recent repository than the Freescale instructions would have but it still contains 2.6.35.3.