drm/amd/display: Update DPG test pattern programming

[Why]
Last ODM slice could be slightly larger than other slice because it can be
including the residual.

[How]
Update DPG pattern programming sequence to use a different width for
last odm slice.

Reviewed-by: Chris Park <chris.park@amd.com>
Acked-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Wenjing Liu <wenjing.liu@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>