meta-ibm: Mihawk use negative-errno-on-fail config

Enable this config for mihawk so the fan sensors are working, otherwise
hwmon will fail and exit when fans are not working.

Tested: Verify that the fan_tach sensors return -ETIMEOUT when host is
        powered off and do not exit with failure.

Signed-off-by: Ben Pai <Ben_Pai@wistron.com>
Change-Id: I5b808183afcdb193ea39d7cd91e978a7902a4d34
diff --git a/meta-witherspoon/recipes-phosphor/sensors/phosphor-hwmon_%.bbappend b/meta-witherspoon/recipes-phosphor/sensors/phosphor-hwmon_%.bbappend
index 420c0e0..4d60a74 100644
--- a/meta-witherspoon/recipes-phosphor/sensors/phosphor-hwmon_%.bbappend
+++ b/meta-witherspoon/recipes-phosphor/sensors/phosphor-hwmon_%.bbappend
@@ -1,5 +1,7 @@
 FILESEXTRAPATHS_prepend := "${THISDIR}/${PN}:"
 
+EXTRA_OECONF_append_mihawk = " --enable-negative-errno-on-fail"
+
 SRC_URI_append_ibm-ac-server = " \
            file://70-hwmon.rules \
            file://70-max31785-hwmon.rules \