drm/amd/display: Reorder dc_state fields to optimize clearing the struct

[why & how]
By moving bw_ctx field to the end of the dc_state the state can be
cleared more efficiently without resulting in large DML memcpy
operations, resulting in better mode enumeration performance on some
platforms.

Acked-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Signed-off-by: Aric Cyr <aric.cyr@amd.com>
Reviewed-by: Nevenko Stupar <Nevenko.Stupar@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>