meta-phosphor: prep for new override syntax

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I588025b614416c43aa2d053765ab53bacf890cb5
diff --git a/meta-phosphor/recipes-phosphor/srvcfg-manager/srvcfg-manager_git.bb b/meta-phosphor/recipes-phosphor/srvcfg-manager/srvcfg-manager_git.bb
index f2be54c..fd43707 100644
--- a/meta-phosphor/recipes-phosphor/srvcfg-manager/srvcfg-manager_git.bb
+++ b/meta-phosphor/recipes-phosphor/srvcfg-manager/srvcfg-manager_git.bb
@@ -15,7 +15,7 @@
 inherit meson pkgconfig systemd
 
 S = "${WORKDIR}/git"
-SYSTEMD_SERVICE_${PN} = "srvcfg-manager.service"
+SYSTEMD_SERVICE:${PN} = "srvcfg-manager.service"
 
 DEPENDS = " \
     boost \