drm/amdgpu: Fix eviction fence worker race during fd close

drm/amdgpu: Fix eviction fence worker race during fd close

The current cleanup order during file descriptor close can lead to
a race condition where the eviction fence worker attempts to access
a destroyed mutex from the user queue manager:

[  517.294055] DEBUG_LOCKS_WARN_ON(lock->magic != lock)
[  517.294060] WARNING: CPU: 8 PID: 2030 at kernel/locking/mutex.c:564
[  517.294094] Workqueue: events amdgpu_eviction_fence_suspend_worker [amdgpu]

The issue occurs because:
1. We destroy the user queue manager (including its mutex) first
2. Then try to destroy eviction fences which may have pending work
3. The eviction fence worker may try to access the already-destroyed mutex

Fix this by reordering the cleanup to:
1. First mark the fd as closing and destroy eviction fences,
   which flushes any pending work
2. Then safely destroy the user queue manager after we're certain
   no more fence work will be executed

The copy in amdgpu_driver_postclose_kms() needs to be removed (Christian)

Reviewed-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Prike Liang <Prike.Liang@amd.com>
Reviewed-by: Arvind Yadav <Arvind.Yadav@amd.com>
Signed-off-by: Jesse Zhang <Jesse.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>