drm/amd/display: Fix DML tests

[Why]
DML diags tests are failing because the struct contents get
clobbered by a memcpy.

[How]
Remove the memcpy call.

Signed-off-by: Ilya Bakoulin <Ilya.Bakoulin@amd.com>
Reviewed-by: Dmytro Laktyushkin <Dmytro.Laktyushkin@amd.com>
Acked-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>