drm/amd/display: Remove unnecessary variable

drm/amd/display: Remove unnecessary variable

There is no need to use dc_version in the dc_construct_ctx since this
value is copied to dc_ctx->dce_version later. This commit removes the
extra steps.

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