accel/amdxdna: Fix notifier_wq lifetime race during device removal

accel/amdxdna: Fix notifier_wq lifetime race during device removal

amdxdna_remove() destroys notifier_wq. If amdxdna_gem_obj_free() is
called after device removal, it may attempt to flush notifier_wq,
resulting in a use-after-free.

Fix the race by allocating notifier_wq with
drmm_alloc_ordered_workqueue(), so its lifetime is managed by DRM and
remains valid until all managed resources are released.

Fixes: e486147c912f ("accel/amdxdna: Add BO import and export")
Reviewed-by: Mario Limonciello (AMD) <superm1@kernel.org>
Signed-off-by: Lizhi Hou <lizhi.hou@amd.com>
Link: https://patch.msgid.link/20260611055150.3070216-2-lizhi.hou@amd.com