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
Merged-In: Iad3b84d9bdf5d8e789219126c88701bf969253ef
(cherry picked from commit 2e86fa0e81d15f5083243f97da32292b742498ca)
1 file changed