Repo-wide replacement to use newer variable to represent systemd
system unitdir directory.
(From OE-Core rev: 5ace3ada5c54500c71becc8e0c6eddeb8bc053e3)
Signed-off-by: Robert P. J. Day <rpjday@crashcourse.ca>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>