linux: kernel-compilation: use kernel release tarball from github

On kernel.org, seems only the latest release tarballs are availabe
for downloading. The following link is invalid now as 4.4.126 has
been released.

  https://cdn.kernel.org/pub/linux/kernel/v4.x/linux-4.4.34.tar.xz

For this test purpose, we just need a fixed release that availabe for a
long time, it doesn't have to be the latest version.

Moving to https://github.com/torvalds/linux/releases seems to be a
simpler and more reliable approach.

Change-Id: I3a9dd003f5a70b1e34d2e82489196c9297eb534b
Signed-off-by: Chase Qi <chase.qi@linaro.org>
2 files changed