drm/amd/amdgpu: SRIOV full reset issue with VCN

- After a full reset, VF's FB will be cleaned. This
  includes the VCN's fw_shared memory.

  However, there is no suspend-resume routine for
  SRIOV VF. Therefore, the data in the fw_shared
  memory will be lost forever and it causes engine
  hang later on.

  We must repopulate the data in fw_shared during
  SRIOV hw_init

Signed-off-by: Bokun Zhang <bokun.zhang@amd.com>
Reviewed-by: Emily Deng <Emily.Deng@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>