drm/amdkfd: remove hardcoded device_info structs

With device_info initialization being handled in kfd_device_info_init,
these structs may be removed. Also add comments to help matching IP
versions to asic names.
Signed-off-by: Graham Sider <Graham.Sider@amd.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>