Adding /debug_ramdisk mount point

This change allows first-stage init to mount a tmpfs under
/debug_ramdisk to preserve files from the debug ramdisk, for
second-stage init to load sepolicy and property files.

This is to allow adb root on a USER build if the device is unlocked.

Bug: 126493225
Test: boot a device with debug ramdisk, checks related files are loaded
Change-Id: Iad3b84d9bdf5d8e789219126c88701bf969253ef
diff --git a/private/file_contexts b/private/file_contexts
index 9785ffb..4f0690b 100644
--- a/private/file_contexts
+++ b/private/file_contexts
@@ -24,6 +24,7 @@
 /lost\+found        u:object_r:rootfs:s0
 /acct               u:object_r:cgroup:s0
 /config             u:object_r:rootfs:s0
+/debug_ramdisk      u:object_r:tmpfs:s0
 /mnt                u:object_r:tmpfs:s0
 /postinstall        u:object_r:postinstall_mnt_dir:s0
 /postinstall/apex   u:object_r:postinstall_apex_mnt_dir:s0