drm/amdgpu: recover vram bo from shadow after gpu reset V2

V2:
1. don't directly submit to many jobs at the same time.
2. delete unrelated printk.

Signed-off-by: Chunming Zhou <David1.Zhou@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>