meta-ampere: phosphor-sel-logger: Use packageconfig

This makes it possible for us to change out build specific settings.

Change-Id: I862366d8efa97c4c3181b842662bf28dd5bec270
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/meta-ampere/meta-common/recipes-phosphor/sel-logger/phosphor-sel-logger_%.bbappend b/meta-ampere/meta-common/recipes-phosphor/sel-logger/phosphor-sel-logger_%.bbappend
index 4be8ddb..2f74fd2 100644
--- a/meta-ampere/meta-common/recipes-phosphor/sel-logger/phosphor-sel-logger_%.bbappend
+++ b/meta-ampere/meta-common/recipes-phosphor/sel-logger/phosphor-sel-logger_%.bbappend
@@ -1,2 +1 @@
-# Enable threshold monitoring
-EXTRA_OECMAKE += "-DSEL_LOGGER_MONITOR_THRESHOLD_EVENTS=ON"
+PACKAGECONFIG_append = " log-threshold"