drm/amdgpu: Fix use of interruptible waiting

1. The signal interrupt can affect the expected behaviour.
2. There is no mechanism to handle the corresponding error.

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>