drm/amd/display: dc/core: add SI/DCE6 support (v2)

drm/amd/display: dc/core: add SI/DCE6 support (v2)

[Why]
resource_parse_asic_id() and dc_create_resource_pool() are missing SI/DCE6 cases

[How]
SI/DCE6 cases support added using existing DCE8 implementation as a reference

(v2) updated due to following kernel 5.2 commit:
     2874240 ("drm/amd/display: Pass init_data into DCN resource creation")

Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Mauro Rossi <issor.oruam@gmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>