drm/amd/display: Remove unused code

drm/amd/display: Remove unused code

[why]
two sets of dccg_init:
one in dc/dccg, one in dc/hwss.
remove hwss's dccg_init for asics not use it.

Reviewed-by: Chris Park <chris.park@amd.com>
Reviewed-by: Dillon Varone <dillon.varone@amd.com>
Signed-off-by: Charlene Liu <Charlene.Liu@amd.com>
Signed-off-by: Ilya Bakoulin <Ilya.Bakoulin@amd.com>
Signed-off-by: Matthew Stewart <matthew.stewart2@amd.com>
Tested-by: Dan Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>