mariadb: use ${PN} for SYSTEMD_AUTO_ENABLE
mariadb: use ${PN} for SYSTEMD_AUTO_ENABLE

Use ${PN} instead of hardcoding 'mariadb' so that everything works
fine in case of multilib.

(master rev: eaa30d4772fd31f1aba17d63486db4c81d8f1804)

Signed-off-by: Chen Qi <633505cc1c1ae5749a9636f0ba75c172681d2e11@windriver.com>
Signed-off-by: Martin Jansa <516df3ff67e1fa5d153800b15fb204c0a1a389dc@gmail.com>
Signed-off-by: Mark Hatle <41765ab18fb75e64ff0efe27f2ebcdb2d6f7e44e@windriver.com>

WindRiver-OpenSourceLabs/meta-oe-subset,WindRiver-OpenSourceLabs/meta-oe-subset