Add EXTRA_IFACES to power supply configurations

Adding support for multiple interface associtions for
inventory items.

Testing: Verifed that the interface was associated properly.

Signed-off-by: Anthony Wilson <wilsonan@us.ibm.com>
Change-Id: Ia7b29b3cc498e8ebc955228a46e4ff2ecb16c55f
diff --git a/meta-witherspoon/recipes-phosphor/gpio/phosphor-gpio-monitor/witherspoon/obmc/gpio/phosphor-power-supply-1.conf b/meta-witherspoon/recipes-phosphor/gpio/phosphor-gpio-monitor/witherspoon/obmc/gpio/phosphor-power-supply-1.conf
index 56e16c5..d7681f8 100644
--- a/meta-witherspoon/recipes-phosphor/gpio/phosphor-gpio-monitor/witherspoon/obmc/gpio/phosphor-power-supply-1.conf
+++ b/meta-witherspoon/recipes-phosphor/gpio/phosphor-gpio-monitor/witherspoon/obmc/gpio/phosphor-power-supply-1.conf
@@ -3,3 +3,4 @@
 KEY=127
 NAME=powersupply1
 DRIVERS=/sys/bus/i2c/drivers/ibm-cffps,3-0068
+EXTRA_IFACES=xyz.openbmc_project.Inventory.Item.PowerSupply