meta-p8 systems: Fix phosphor-gpio-monitor crash

The P8 systems use different GPIOs for checkstop, and cause
phosphor-gpio-monitor crash.
Define correct GPIO key for each P8 systems to fix the issue.

Fixes openbmc/openbmc#2349

Change-Id: I5f8dd79e17971091e799f9498959b307f03702b6
Signed-off-by: Lei YU <mine260309@gmail.com>
diff --git a/meta-openbmc-machines/meta-openpower/meta-rackspace/meta-barreleye/recipes-phosphor/host/checkstop-monitor.bbappend b/meta-openbmc-machines/meta-openpower/meta-rackspace/meta-barreleye/recipes-phosphor/host/checkstop-monitor.bbappend
new file mode 100644
index 0000000..72d991c
--- /dev/null
+++ b/meta-openbmc-machines/meta-openpower/meta-rackspace/meta-barreleye/recipes-phosphor/host/checkstop-monitor.bbappend
@@ -0,0 +1 @@
+FILESEXTRAPATHS_prepend := "${THISDIR}/${PN}:"