drm/amd/display: Use unbound workqueues for deferred DM work

drm/amd/display: Use unbound workqueues for deferred DM work

DM currently queues some deferred display work on system workqueues.
Low-context IRQ handlers are queued on system_highpri_wq, while deferred
vmin/vmax updates are queued on system_percpu_wq.

Both paths can execute long-running display work. HPD and HPD RX handling
may involve link detection, AUX transactions, connector state updates, and
hotplug notification. The vmin/vmax update path calls into DC under
dc_lock to adjust stream timing. These paths can therefore trigger the
workqueue CPU hog detector when run from per-CPU workers:

  workqueue: dm_irq_work_func [amdgpu] hogged CPU for >10000us
  workqueue: dm_handle_vmin_vmax_update [amdgpu] hogged CPU for >10000us

Move the deferred low-context IRQ work to a dedicated high-priority
unbound workqueue, preserving the priority of the previous
system_highpri_wq usage while avoiding long-running work on per-CPU
workers.

Move deferred vmin/vmax updates to a separate normal-priority unbound
workqueue.

High-context IRQ handlers remain unchanged and continue to run directly
from the IRQ path.

Signed-off-by: Geoffrey McRae <geoffrey.mcrae@amd.com>
Reviewed-by: Leo Li <sunpeng.li@amd.com>
Cc: Harry Wentland <harry.wentland@amd.com>
Cc: Leo Li <sunpeng.li@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>