Revert "Revert "Move ramdisk to the new init_boot partition""

This reverts commit 3c76abb8ea0c3c95e53a38c13c9e29791e0f10ae.

Reason for revert: Presubmits should now pass with fixed u-boot prebuilts

Change-Id: I5f60c10640cd19ee2ed4b874a077c1596a53e612
diff --git a/microdroid/microdroid.json b/microdroid/microdroid.json
index 8496052..9e630f8 100644
--- a/microdroid/microdroid.json
+++ b/microdroid/microdroid.json
@@ -8,6 +8,10 @@
           "path": "/apex/com.android.virt/etc/fs/microdroid_boot-5.10.img"
         },
         {
+          "label": "init_boot_a",
+          "path": "/apex/com.android.virt/etc/fs/microdroid_init_boot.img"
+        },
+        {
           "label": "vendor_boot_a",
           "path": "/apex/com.android.virt/etc/fs/microdroid_vendor_boot-5.10.img"
         },