airoha: an7581: Set eMMC overlay to symlink /tmp/rootfs_data

airoha/an7581/base-files/etc/system_layout/emmc.json

@@ -4,13 +4,13 @@
       "id": 1,
       "name": "A",
       "rootfs": "/dev/mmcblk0p65",
-      "overlay": "/dev/mmcblk0p66"
+      "overlay": "/tmp/rootfs_data1"
     },
     {
       "id": 2,
       "name": "B",
       "rootfs": "/dev/mmcblk0p67",
-      "overlay": "/dev/mmcblk0p68"
+      "overlay": "/tmp/rootfs_data2"
     }
   ],
   "overlay_scope": [