drm/amdgpu/gfx10: require to pin/unpin CSIB BO when suspend/resume

CSIB BO is required to be pinned down to guarantee
bo is always valid when resume, and to be unpinned it
so that its content can be saved during suspend.

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