doc only: Correct fan presence recipe comment

Change-Id: I16ce78cec0e322852de40a533ac0e961af31017d
Signed-off-by: Matthew Barth <msbarth@us.ibm.com>
diff --git a/recipes-phosphor/fans/phosphor-fan-presence-config.bb b/recipes-phosphor/fans/phosphor-fan-presence-config.bb
index 30da6ea..d4176c5 100644
--- a/recipes-phosphor/fans/phosphor-fan-presence-config.bb
+++ b/recipes-phosphor/fans/phosphor-fan-presence-config.bb
@@ -1,7 +1,7 @@
 # Provides the config file for the phosphor-fan-presence application.
 # The default config file is empty.  To provide a real one,
 # append this recipe in a layer, add:
-# FILESEXTRAPATHS_prepend := "${THISDIR}/${PN}:"
+# FILESEXTRAPATHS_prepend := "${THISDIR}/${BPN}:"
 # and provide a config file.
 
 SUMMARY = "Config file for phosphor-fan-presence"