drm/amd/display: Set stream's DP test pattern upon test request

[Why]
A recent refactor of DC's DP test pattern automation code requires the
DC stream's test pattern and test pattern color space fields to be
correctly populated before calling dc_link_dp_set_test_pattern.

[How]
Populate stream's test pattern type and color space fields before
calling into DC to program DP test pattern.

Reviewed-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Acked-by: Hersen Wu <hersenxs.wu@amd.com>
Signed-off-by: George Shen <george.shen@amd.com>
Signed-off-by: Hersen Wu <hersenxs.wu@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>