Modify mako script to generate code for empty interfaces

Allow generating empty interfaces in the FRU map, which are
used to determine the type of the inventory object.

Change-Id: I6dc97514b0bdf7ef9d3a63ee6790a7933b3e7cd9
Signed-off-by: Marri Devender Rao <devenrao@in.ibm.com>
diff --git a/scripts/fru-read-example.yaml b/scripts/fru-read-example.yaml
index 8c6074c..86151af 100644
--- a/scripts/fru-read-example.yaml
+++ b/scripts/fru-read-example.yaml
@@ -33,6 +33,7 @@
       Version:
         IPMIFruProperty: Version
         IPMIFruSection: Product
+    xyz.openbmc_project.Inventory.Item.System:
 1:
   /system/chassis/motherboard/dimm0:
     xyz.openbmc_project.Inventory.Item:
@@ -56,6 +57,7 @@
       Version:
         IPMIFruProperty: Version
         IPMIFruSection: Product
+    xyz.openbmc_project.Inventory.Item.Dimm:
 2:
   /system/chassis/motherboard/dimm1:
     xyz.openbmc_project.Inventory.Item:
@@ -79,6 +81,7 @@
       Version:
         IPMIFruProperty: Version
         IPMIFruSection: Product
+    xyz.openbmc_project.Inventory.Item.Dimm:
 3:
   /system/chassis/motherboard/cpu0:
     xyz.openbmc_project.Inventory.Item:
@@ -98,6 +101,7 @@
       Manufacturer:
         IPMIFruProperty: Manufacturer
         IPMIFruSection: Board
+    xyz.openbmc_project.Inventory.Item.Cpu:
 4:
   /system/chassis/motherboard/cpu1:
     xyz.openbmc_project.Inventory.Item:
@@ -117,3 +121,4 @@
       Manufacturer:
         IPMIFruProperty: Manufacturer
         IPMIFruSection: Board
+    xyz.openbmc_project.Inventory.Item.Cpu: