libatomic_ops: Update repository and bump version

Change the download source to a Github repository which is more recent.
This patch also bump libatomic_ops version and remove a patch that is
now upstream.

Signed-off-by: Maxime Hadjinlian <maxime.hadjinlian@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>