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/dump/debug-trigger_git.bb b/meta-phosphor/recipes-phosphor/dump/debug-trigger_git.bb
index dd28e0f..fbb41f2 100644
--- a/meta-phosphor/recipes-phosphor/dump/debug-trigger_git.bb
+++ b/meta-phosphor/recipes-phosphor/dump/debug-trigger_git.bb
@@ -31,4 +31,4 @@
     -Dtriggers=[], \
     systemd udev"
 
-SYSTEMD_SERVICE_${PN} += "debug-trigger@.service"
+SYSTEMD_SERVICE:${PN} += "debug-trigger@.service"