Revert "drm/msm: Clean up dangling atomic_wq"

This reverts commit 74312fc7.

This reversion is happening as a result of disabling the
disp/dpu directory as it will not be used in 4.19 downstream
display driver and these changes are made in a common layer
which affects the downstream driver functionalities. Separate
patches are submitted to revert the upstream driver and
introduce the downstream version of the display driver.

Change-Id: I18ac33a3d1f11ffd48dfd95f5e89bfd4a6fcdc3c
Signed-off-by: Samantha Tran <samtran@codeaurora.org>