Revert "drm/msm: Add .commit() callback to msm_kms functions"

This reverts commit 2b7ac1a8.

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: I8eab96d532894ad63e9032140b5958e5704a1429
Signed-off-by: Samantha Tran <samtran@codeaurora.org>