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/busybox/busybox_%.bbappend b/meta-phosphor/recipes-core/busybox/busybox_%.bbappend
index 9433b5c..a64c144 100644
--- a/meta-phosphor/recipes-core/busybox/busybox_%.bbappend
+++ b/meta-phosphor/recipes-core/busybox/busybox_%.bbappend
@@ -1,4 +1,4 @@
-FILESEXTRAPATHS_prepend := "${THISDIR}/${PN}:"
+FILESEXTRAPATHS:prepend := "${THISDIR}/${PN}:"
 SRC_URI += "file://busybox.cfg"
 SRC_URI += "file://flash.cfg"
 SRC_URI += "file://less.cfg"