drm/amdgpu: add amdgpu_smuio structure

Add amdgpu_smuio structure in amdgpu_device to
provide various callback functions to support
smuio ip funcitonality

Signed-off-by: Hawking Zhang <Hawking.Zhang@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: John Clements <john.clements@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>