VCN shared memory needs restore after wake up during S3 test.

v2: Allocate shared memory saved_bo at sw_init and free it in sw_fini.
Signed-off-by: NJames Zhu <James.Zhu@amd.com>
Reviewed-by: NFeifei Xu <Feifei.Xu@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>