Revert "drm/amdgpu/display: set vblank_disable_immediate for DC"

This reverts commit 92020e81.

This causes stuttering and timeouts with DMCUB for some users
so revert it until we understand why and safely enable it
to save power.

Bug: drm/amd#1887


Acked-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>