Revert "drm/msm: Add pm_suspend/resume callbacks to msm_kms"

This reverts commit 036bfeb3.

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: Ia73dec565f1def7eeb36077c3eb140cd1f1393eb
Signed-off-by: Samantha Tran <samtran@codeaurora.org>