Add Depth component enum for images (#407)

Signed-off-by: Aravind Gopalakrishnan <aravind.gopalakrishnan@intel.com>

Author: aravindksg

scripts/core/image.yml

@@ -174,6 +174,8 @@ etors:
       desc: "One"
     - name: X
       desc: "Don't care"
+    - name: D
+      desc: "Depth Component"
 --- #--------------------------------------------------------------------------
 type: struct
 desc: "Image format "