drm/amd/display: Set max TTU on DPG enable

[WHY]
There is a bug in HW that causes P-State to hang when DPG is enabled in
certain conditions.

[HOW]
The solution is to force MIN_TTU_VBLANK register to maximum value
whenever DPG has been enabled.
Make stream do a full update on test pattern change, so that the TTUs
get updated.
When DPG is enabled, update the ttu_regs.min_ttu_vblank field of each
pipe in the stream's topology to the maximum value (0xffffff).

v2: squash in build fix for when DCN is not defined (Alex)

Signed-off-by: Wesley Chalmers <Wesley.Chalmers@amd.com>
Reviewed-by: Tony Cheng <Tony.Cheng@amd.com>
Acked-by: Anson Jacob <Anson.Jacob@amd.com>
Tested-by: Dan Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>