Revert "drm/msm: Add SDM845 DPU support"

This reverts commit 25fdd593.

DPU will not be used in 4.19 downstream display driver code.
Separate patches are submitted to introduce the downstream
version of the display driver.

Change-Id: I7230a55c502f1d62a889770728c25394c7d0dcd3
Signed-off-by: Samantha Tran <samtran@codeaurora.org>