swift: Add fan-presence and fan-monitor

Swift fails to build because fan-presence is a dependency for
fan-control, and fan-monitor is a dependency for inventory.
So add them in swift with an empty yaml file. Also fix the
FILESEXTRAPATHS_append to have the colon at the beginning
(vs prepend where colon goes at the end) to be able to find
the files in the right order.

Tested: Built swift successfully.

Change-Id: I28fdfdd90f7935eb072d2fdfaa207517701ebbb3
Signed-off-by: Adriana Kobylak <anoo@us.ibm.com>
diff --git a/meta-witherspoon/recipes-phosphor/fans/swift-phosphor-fan-presence-config-native/config.yaml b/meta-witherspoon/recipes-phosphor/fans/swift-phosphor-fan-presence-config-native/config.yaml
new file mode 100644
index 0000000..5b9856c
--- /dev/null
+++ b/meta-witherspoon/recipes-phosphor/fans/swift-phosphor-fan-presence-config-native/config.yaml
@@ -0,0 +1,2 @@
+# TODO: Populate with https://github.com/ibm-openbmc/dev/issues/601
+# Placeholder