drm/amd/display: Use provided offset for DPG generation

[Why]
Currently, the offset provided to dcn30_set_disp_pattern_generator is
not forwarded to OPP for display pattern generation, resulting in
misaligned patterns and test failures.

[How]
Use the provided offset.

Signed-off-by: Wesley Chalmers <Wesley.Chalmers@amd.com>
Reviewed-by: Samson Tam <Samson.Tam@amd.com>
Acked-by: Eryk Brol <eryk.brol@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>