Make system-as-root a phone-specific thing

Test: auto builds, boots
BUG: 110695415
Change-Id: Iffe8863e0a99e1dccb3325a6e5004e44a93e68f1
Merged-In: Iffe8863e0a99e1dccb3325a6e5004e44a93e68f1
(cherry picked from commit 512dad95b77e734435ce91043a2c1424d66eed19)
diff --git a/shared/config/initrd-root.dtb b/shared/config/initrd-root.dtb
index bdffbc7..1c75cd6 100644
--- a/shared/config/initrd-root.dtb
+++ b/shared/config/initrd-root.dtb
Binary files differ
diff --git a/shared/config/initrd-root.dts b/shared/config/initrd-root.dts
index d0dedbe..70a34fc 100644
--- a/shared/config/initrd-root.dts
+++ b/shared/config/initrd-root.dts
@@ -22,6 +22,14 @@
 			compatible = "android,firmware";
 			fstab {
 				compatible = "android,fstab";
+				system {
+					compatible = "android,system";
+					dev = "/dev/block/vda";
+					type = "ext4";
+					mnt_flags = "noatime,ro,errors=panic";
+					fsmgr_flags = "wait";
+				};
+
 				vendor {
 					compatible = "android,vendor";
 					dev = "/dev/block/vdd";