meta-phosphor: prep for new override syntax

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I588025b614416c43aa2d053765ab53bacf890cb5
diff --git a/meta-phosphor/classes/phosphor-dbus-yaml.bbclass b/meta-phosphor/classes/phosphor-dbus-yaml.bbclass
index 973c2bd..b42b349 100644
--- a/meta-phosphor/classes/phosphor-dbus-yaml.bbclass
+++ b/meta-phosphor/classes/phosphor-dbus-yaml.bbclass
@@ -1,4 +1,4 @@
 yaml_dir = "${datadir}/phosphor-dbus-yaml/yaml"
 
 PACKAGE_BEFORE_PN += "${PN}-yaml"
-FILES_${PN}-yaml += "${yaml_dir}"
+FILES:${PN}-yaml += "${yaml_dir}"