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/Android.bp b/microdroid/Android.bp
index 3eaf124..6c96cbf 100644
--- a/microdroid/Android.bp
+++ b/microdroid/Android.bp
@@ -221,7 +221,6 @@
 
 bootimg {
     name: "microdroid_boot-5.10",
-    ramdisk_module: "microdroid_ramdisk-5.10",
     // We don't have kernel for arm and x86. But Soong demands one when it builds for
     // arm or x86 target. Satisfy that by providing an empty file as the kernel.
     kernel_prebuilt: "empty_kernel",
@@ -251,6 +250,16 @@
     avb_private_key: ":microdroid_sign_key",
 }
 
+bootimg {
+    name: "microdroid_init_boot",
+    ramdisk_module: "microdroid_ramdisk-5.10",
+    kernel_prebuilt: "empty_kernel",
+    header_version: "4",
+    partition_name: "init_boot",
+    use_avb: true,
+    avb_private_key: ":microdroid_sign_key",
+}
+
 android_filesystem {
     name: "microdroid_ramdisk-5.10",
     deps: [
@@ -551,6 +560,7 @@
         "microdroid_vendor_boot-5.10",
         "microdroid",
         "microdroid_boot-5.10",
+        "microdroid_init_boot",
     ],
 }