drm/amdgpu: Add XCP functions for GFX v9.4.3

Add functions to suspend/resume GFX instances belonging to an XCP.

Signed-off-by: Lijo Lazar <lijo.lazar@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>