meta-zaius: checkstop-monitor: add machine suffix

For checkstop-monitor, add zaius machine suffix to avoid poisoning other
machines using this layer.

Change-Id: I4c513aaaaf4a8440f8622962be77babd851ff09b
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/meta-zaius/recipes-phosphor/host/checkstop-monitor.bbappend b/meta-zaius/recipes-phosphor/host/checkstop-monitor.bbappend
index 72d991c..2072afd 100644
--- a/meta-zaius/recipes-phosphor/host/checkstop-monitor.bbappend
+++ b/meta-zaius/recipes-phosphor/host/checkstop-monitor.bbappend
@@ -1 +1 @@
-FILESEXTRAPATHS_prepend := "${THISDIR}/${PN}:"
+FILESEXTRAPATHS_prepend_zaius := "${THISDIR}/${PN}:"