meta-facebook: prep for new override syntax

Ran `scripts/contrib/convert-overrides.py` from upstream Yocto and
fixed up a few by hand that were missed.

Tested: Built bletchley and tiogapass.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I0489ba007132901697e4ef1a29b03a3591b3ee3b
diff --git a/meta-facebook/recipes-x86/chassis/x86-power-control_%.bbappend b/meta-facebook/recipes-x86/chassis/x86-power-control_%.bbappend
index aa99b7e..c119bac 100644
--- a/meta-facebook/recipes-x86/chassis/x86-power-control_%.bbappend
+++ b/meta-facebook/recipes-x86/chassis/x86-power-control_%.bbappend
@@ -1,2 +1,2 @@
-FILESEXTRAPATHS_prepend := "${THISDIR}/${PN}:"
+FILESEXTRAPATHS:prepend := "${THISDIR}/${PN}:"
 EXTRA_OECMAKE += "-DCHASSIS_SYSTEM_RESET=ON"