storage: turn off writebooster flags upon init

Enabling writebooster capability for Pixel UFS (pa/2994670)
enabled the following flags in Android Common Kernel:

  - wb_flush_en
  - wb_flush_during_h8
  - wb_enable

This patch disables these writebooster-related flags to restore the
intended behavior for Pixel devices. This overrides the default Android
Common Kernel behavior.

While 'wb_flush_en' and 'wb_enable' have corresponding sysfs entries
('enable_wb_buf_flush' and 'wb_on') for toggling,
'wb_flush_during_h8' currently lacks this functionality in the Android
Common Kernel. Pixel provides the 'manual_gc' sysfs entry as a
workaround. Setting 'manual_gc' to 0 disables 'wb_flush_during_h8'.

Bug: 377958570
Flag: EXEMPT bugfix
Test: check if all writebooster-realated flags are false upon init
Change-Id: I918bf6939de3e208b715f554a96ccbd053f68a18
Signed-off-by: Daniel Lee <chullee@google.com>

storage/init.storage.rc

@@ -42,10 +42,13 @@ on init
 
     # UFS
     write /dev/sys/block/bootdevice/clkgate_enable 0
+    write /dev/sys/block/bootdevice/wb_on 0
+    write /dev/sys/block/bootdevice/enable_wb_buf_flush 0
 
 on property:sys.boot_completed=1
     # Health Storage HAL
     chown system system /dev/sys/block/bootdevice/manual_gc
+    write /dev/sys/block/bootdevice/manual_gc 0
 
     # Pixelstats
     chown system system /dev/sys/block/bootdevice/slowio_read_cnt