Remove old busybox directory and use upstream submodule instead.
Update upstream to point to 1_29_3 tag.
Include busybox-sailfish.config as a source file.
Add a patch from git history that we used to have with the old version
because it is still not part of upstream version.
Update spec to match the new version with the patch.
Signed-off-by: Tomi Leppänen <firstname.lastname@example.org>