DEVPATH fix for phosphor-gpio-monitor@checkstop.service

This commit fixes an error introduced by openbmc/openbmc#2149 in
which phosphor-gpio-monitor@checkstop.service would fail because
the file /etc/default/obmc/gpio/checkstop defines PATH and not
DEVPATH. PATH is, of course, an environment variable that should
not be changed.

The problem is fixed by updating the defintion in this file from
PATH to DEVPATH.

Resolves openbmc/openbmc#2216

Change-Id: I941c0c1315e49abd21daceb5b9f9e7719b5cb0bf
Signed-off-by: Michael Tritz <mtritz@us.ibm.com>
diff --git a/meta-openbmc-machines/meta-openpower/common/recipes-phosphor/host/checkstop-monitor/obmc/gpio/checkstop b/meta-openbmc-machines/meta-openpower/common/recipes-phosphor/host/checkstop-monitor/obmc/gpio/checkstop
index e6468d8..e856339 100644
--- a/meta-openbmc-machines/meta-openpower/common/recipes-phosphor/host/checkstop-monitor/obmc/gpio/checkstop
+++ b/meta-openbmc-machines/meta-openpower/common/recipes-phosphor/host/checkstop-monitor/obmc/gpio/checkstop
@@ -1,4 +1,4 @@
-PATH=/dev/input/by-path/platform-gpio-keys-event
+DEVPATH=/dev/input/by-path/platform-gpio-keys-event
 KEY=74
 POLARITY=1
 TARGET=obmc-host-crash@0.target