drm/amdgpu: Fix use of interruptible waiting

Either in cgs functions or for callers of cgs functions:
1. The signal interrupt can affect the expected behaviour
2. There is no good mechanism to handle the corresponding error
3. There is no chance of deadlock in these single BO waiting
4. There is no clear benefit for interruptible waiting
5. Future caller of these functions might have same issue.

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