meta-phosphor: prep for new override syntax

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I588025b614416c43aa2d053765ab53bacf890cb5
diff --git a/meta-phosphor/recipes-core/systemd/obmc-targets.bb b/meta-phosphor/recipes-core/systemd/obmc-targets.bb
index a95535e..1063112 100644
--- a/meta-phosphor/recipes-core/systemd/obmc-targets.bb
+++ b/meta-phosphor/recipes-core/systemd/obmc-targets.bb
@@ -11,6 +11,6 @@
     file://obmc-mapper.target \
 "
 
-SYSTEMD_SERVICE_${PN} += " \
+SYSTEMD_SERVICE:${PN} += " \
     obmc-mapper.target \
 "