witherspoon: Use first-boot-set-mac

Use the new first-boot-set-mac recipe from the openpower layer for
setting the mac address on first boot.  This replaces
obmc-mgr-inventory's sync_inventory_items.py script that achieves the
same - but is the last remaining requirement for python on Witherspoon
systems and first-boot-set-mac is shell!

Tested-By: Built a witherspoon image and manually verified the root
           filesystem included a symlink to first-boot-set-mac@.service
           in /etc.
Change-Id: Ib0ced58f7f6d712cb4ffb7bd062d28e727b5dcb1
Signed-off-by: Brad Bishop <bradleyb@fuzziesquirrel.com>
diff --git a/meta-witherspoon/recipes-phosphor/network/first-boot-set-mac_%.bbappend b/meta-witherspoon/recipes-phosphor/network/first-boot-set-mac_%.bbappend
new file mode 100644
index 0000000..29d23c8
--- /dev/null
+++ b/meta-witherspoon/recipes-phosphor/network/first-boot-set-mac_%.bbappend
@@ -0,0 +1 @@
+SYSTEMD_SERVICE_${PN} += "first-boot-set-mac@eth0.service"