drm/amd/display: Fix incorrect pointer assignment

[Why]
Pointer initialization and assignment for dml2_options is not done
correctly. While this works for some compilers, others give an error.

[How]
Modify dc_state_create code to correctly initialize the dml2_opt pointer
and pass it to dml2_create. Also update the code with correct derefrence
operations.

Reviewed-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Acked-by: Rodrigo Siqueira <rodrigo.siqueira@amd.com>
Signed-off-by: Chaitanya Dhere <chaitanya.dhere@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>