drm/amdgpu: fix userq hang detection and reset

drm/amdgpu: fix userq hang detection and reset

Fix lock inversions pointed out by Prike and Sunil. The hang detection
timeout *CAN'T* grab locks under which we wait for fences, especially
not the userq_mutex lock.

Then instead of this completely broken handling with the
hang_detect_fence just cancel the work when fences are processed and
re-start if necessary.

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Sunil Khatri <sunil.khatri@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>