meta-sulfur: recipes-core: systemd: Fix sfp swap files
meta-sulfur: recipes-core: systemd: Fix sfp swap files

Make sure the bbappends and FILEPATH_prepend only happens
for ni-sulfur machines.

Signed-off-by: Moritz Fischer <2b469823646c02e9f01a7ad5b893ceac76b06bbe@ettus.com>

EttusResearch/meta-ettus,EttusResearch/meta-ettus,EttusResearch/meta-ettus,EttusResearch/meta-ettus,EttusResearch/meta-ettus,EttusResearch/meta-ettus