[why]
1. Move dd_link_ddc functions to link_ddc.
2. Move link ddc functions declaration exposed in dc to link.h
3. Move link ddc functions declaration exposed in dm to dc_link.h
4. Remove i2caux_interface.h file
Tested-by: NDaniel Wheeler <Daniel.Wheeler@amd.com>
Reviewed-by: NJun Lei <Jun.Lei@amd.com>
Acked-by: NRodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: NWenjing Liu <wenjing.liu@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>