drm/amd/display: Add 3DLUT FL HW bug workaround

[Why]
There is a known HW bug that causes the internal 3DLUT fetch signal to
be lost at VREADY, regardless of whether the OTG lock is being held or
not. A workaround is necessary to make sure that this internal signal
stays up after OTG unlock.

[How]
Set the 3DLUT_ENABLE bit immediately before and after the unlock. Also
use VUPDATE_KEEPOUT to prevent lock transition in the region between
VSTARTUP and VREADY, which could cause issues with this WA sequence.

Also including misc. 3DLUT DMA-related sequence fixes to address a few
regressions causing corruption.

Reviewed-by: Dillon Varone <dillon.varone@amd.com>
Signed-off-by: Ilya Bakoulin <Ilya.Bakoulin@amd.com>
Signed-off-by: Roman Li <roman.li@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>