Revert "bdi: Do not use freezable workqueue"

This reverts commit c801b7e6.

This commit causes devices to randomly freeze on 4.14 and 4.19 kernels.
This happens mostly during suspend. Force restarting the device via button combination leaves no ramoops or logs.

Signed-off-by: UtsavBalar1231 <utsavbalar1231@gmail.com>
Change-Id: I5bc87804724430a5ca85b5563105a79b6f730182