drm/xe: Process deferred GGTT node removals on device unwind

In the Linux kernel, the following vulnerability has been resolved:

drm/xe: Process deferred GGTT node removals on device unwind

While we are indirectly draining our dedicated workqueue ggtt->wq
that we use to complete asynchronous removal of some GGTT nodes,
this happends as part of the managed-drm unwinding (ggtt_fini_early),
which could be later then manage-device unwinding, where we could
already unmap our MMIO/GMS mapping (mmio_fini).

This was recently observed during unsuccessful VF initialization:

[ ] xe 0000:00:02.1: probe with driver xe failed with error -62
[ ] xe 0000:00:02.1: DEVRES REL ffff88811e747340 __xe_bo_unpin_map_no_vm (16 bytes)
[ ] xe 0000:00:02.1: DEVRES REL ffff88811e747540 __xe_bo_unpin_map_no_vm (16 bytes)
[ ] xe 0000:00:02.1: DEVRES REL ffff88811e747240 __xe_bo_unpin_map_no_vm (16 bytes)
[ ] xe 0000:00:02.1: DEVRES REL ffff88811e747040 tiles_fini (16 bytes)
[ ] xe 0000:00:02.1: DEVRES REL ffff88811e746840 mmio_fini (16 bytes)
[ ] xe 0000:00:02.1: DEVRES REL ffff88811e747f40 xe_bo_pinned_fini (16 bytes)
[ ] xe 0000:00:02.1: DEVRES REL ffff88811e746b40 devm_drm_dev_init_release (16 bytes)
[ ] xe 0000:00:02.1: [drm:drm_managed_release] drmres release begin
[ ] xe 0000:00:02.1: [drm:drm_managed_release] REL ffff88810ef81640 __fini_relay (8 bytes)
[ ] xe 0000:00:02.1: [drm:drm_managed_release] REL ffff88810ef80d40 guc_ct_fini (8 bytes)
[ ] xe 0000:00:02.1: [drm:drm_managed_release] REL ffff88810ef80040 __drmm_mutex_release (8 bytes)
[ ] xe 0000:00:02.1: [drm:drm_managed_release] REL ffff88810ef80140 ggtt_fini_early (8 bytes)

and this was leading to:

[ ] BUG: unable to handle page fault for address: ffffc900058162a0
[ ] #PF: supervisor write access in kernel mode
[ ] #PF: error_code(0x0002) - not-present page
[ ] Oops: Oops: 0002 [#1] SMP NOPTI
[ ] Tainted: [W]=WARN
[ ] Workqueue: xe-ggtt-wq ggtt_node_remove_work_func [xe]
[ ] RIP: 0010:xe_ggtt_set_pte+0x6d/0x350 [xe]
[ ] Call Trace:
[ ] <TASK>
[ ] xe_ggtt_clear+0xb0/0x270 [xe]
[ ] ggtt_node_remove+0xbb/0x120 [xe]
[ ] ggtt_node_remove_work_func+0x30/0x50 [xe]
[ ] process_one_work+0x22b/0x6f0
[ ] worker_thread+0x1e8/0x3d

Add managed-device action that will explicitly drain the workqueue
with all pending node removals prior to releasing MMIO/GSM mapping.

(cherry picked from commit 89d2835c3680ab1938e22ad81b1c9f8c686bd391)