drm/amdkfd: process exit and retry fault race

drm/amdkfd: process exit and retry fault race

kfd_process_wq_release drain retry fault to ensure no retry fault comes
after removing kfd process from the hash table, otherwise svm page fault
handler will fail to recover the fault and dump GPU vm fault log.

Refactor deferred list work to get_task_mm and take mmap write lock
to handle all ranges, and avoid mm is gone while inserting mmu notifier.

Signed-off-by: Philip Yang <Philip.Yang@amd.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>