drm/amdgpu: re-structue members for ip discovery

This is to prepare for initializing discovery tmr size per
ASIC type

Signed-off-by: Hawking Zhang <Hawking.Zhang@amd.com>
Reviewed-by: Likun Gao <Likun.Gao@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>