drm/amdgpu: amdgpu_device_recover_vram always failed if only one node in shadow_list

amdgpu_bo_restore_shadow would assign zero to r if succeeded.
r would remain zero if there is only one node in shadow_list.
current code would always return failure when r <= 0.
restart the timeout for each wait was a rather problematic bug as well.
The value of tmo SHOULD be changed, otherwise we wait tmo jiffies on each loop.

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