drm/amdgpu: Use transient mode during xcp switch

During partition switch, keep the state as transient mode. Fetch the
latest state if switch fails.

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>