Defer the ggtt node removal to a thread if runtime_pm is not active.

The ggtt node removal can be called from multiple places, including
places where we cannot protect with outer callers and places we are
within other locks. So, try to grab the runtime reference if the
device is already active, otherwise defer the removal to a separate
thread from where we are sure we can wake the device up.

v2: - use xe wq instead of system wq (Matt and CI)
    - Avoid GFP_KERNEL to be future proof since this removal can
    be called from outside our drivers and we don't want to block
    if atomic is needed. (Brost)
v3: amend forgot chunk declaring xe_device.
v4: Use a xe_ggtt_region to encapsulate the node and remova info,
    wihtout the need for any memory allocation at runtime.
v5: Actually fill the delayed_removal.invalidate (Brost)
v6: - Ensure that ggtt_region is not freed before work finishes (Auld)
    - Own wq to ensures that the queued works are flushed before
      ggtt_fini (Brost)
v7: also free ggtt_region on early !bound return (Auld)
v8: Address the null deref (CI)
v9: Based on the new xe_ggtt_node for the proper care of the lifetime
    of the object.
v10: Redo the lost v5 change. (Brost)
v11: Simplify the invalidate_on_remove (Lucas)

Cc: Matthew Auld <matthew.auld@intel.com>
Cc: Paulo Zanoni <paulo.r.zanoni@intel.com>
Cc: Francois Dugast <francois.dugast@intel.com>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240821193842.352557-12-rodrigo.vivi@intel.comSigned-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>