package/systemd: fix patch order

Rename 0002-install-don-t-use-ln-relative.patch to
0001-install-don-t-use-ln-relative.patch as there is two 0002-xxx
patches

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>