configurations: mtmitchell: Add NetworkInterface

This commit adds `xyz.openbmc_project.Inventory.Item.NetworkInterface`
with the property `MACAddress` to mtjade.json.

Signed-off-by: Chau Ly <chaul@amperecomputing.com>
Change-Id: Iec8c0404d64ab8829e7e85a01e0caef7052fe00e
diff --git a/configurations/mtmitchell_mb.json b/configurations/mtmitchell_mb.json
index 0e10635..d1f0572 100644
--- a/configurations/mtmitchell_mb.json
+++ b/configurations/mtmitchell_mb.json
@@ -2254,6 +2254,9 @@
             "Names": [
                 "com.ampere.Hardware.Chassis.Model.MtMitchell"
             ]
+        },
+        "xyz.openbmc_project.Inventory.Item.NetworkInterface": {
+            "MACAddress": "$BOARD_INFO_AM1"
         }
     }
 ]