microdroid: use a single vbmeta for all partitions

Since we don't need to update partitions separately, a single vbmeta is
enough for all partitions.

Bug: 193504286
Test: atest MicrodroidHostTestCases
Change-Id: I4f0e84dc0132c8f3ff9262e11bfc68eaf7863169
diff --git a/microdroid/Android.bp b/microdroid/Android.bp
index 3665687..4d7c218 100644
--- a/microdroid/Android.bp
+++ b/microdroid/Android.bp
@@ -438,21 +438,6 @@
     partitions: [
         "microdroid_vendor",
         "microdroid_vendor_boot-5.10",
-    ],
-    chained_partitions: [
-        {
-            name: "vbmeta_system",
-            rollback_index_location: 1,
-            private_key: ":avb_testkey_rsa4096",
-        },
-    ],
-}
-
-vbmeta {
-    name: "microdroid_vbmeta_system",
-    partition_name: "vbmeta_system",
-    private_key: ":avb_testkey_rsa4096",
-    partitions: [
         "microdroid",
         "microdroid_boot-5.10",
     ],
diff --git a/microdroid/fstab.microdroid b/microdroid/fstab.microdroid
index f0e70b6..25d82cc 100644
--- a/microdroid/fstab.microdroid
+++ b/microdroid/fstab.microdroid
@@ -1,2 +1,2 @@
-system /system ext4 noatime,ro,errors=panic wait,slotselect,avb=vbmeta_system,first_stage_mount,logical
+system /system ext4 noatime,ro,errors=panic wait,slotselect,avb=vbmeta,first_stage_mount,logical
 vendor /vendor ext4 noatime,ro,errors=panic wait,slotselect,avb=vbmeta,first_stage_mount,logical
diff --git a/microdroid/microdroid.json b/microdroid/microdroid.json
index 1337edf..211bae4 100644
--- a/microdroid/microdroid.json
+++ b/microdroid/microdroid.json
@@ -16,10 +16,6 @@
           "path": "/apex/com.android.virt/etc/fs/microdroid_vbmeta.img"
         },
         {
-          "label": "vbmeta_system_a",
-          "path": "/apex/com.android.virt/etc/fs/microdroid_vbmeta_system.img"
-        },
-        {
           "label": "super",
           "path": "/apex/com.android.virt/etc/fs/microdroid_super.img"
         }