systemd: include /etc/rpm/macros.systemd in PN-dev

* fixes:
  WARNING: QA Issue: systemd: Files/directories were installed but not shipped
    /etc/rpm
    /etc/rpm/macros.systemd

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>
Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>