drm/xe: Skip exec queue schedule toggle if queue is idle during suspend

drm/xe: Skip exec queue schedule toggle if queue is idle during suspend

If an exec queue is idle, there is no need to issue a schedule disable
to the GuC when suspending the queue’s execution. Opportunistically skip
this step if the queue is idle and not a parallel queue. Parallel queues
must have their scheduling state flipped in the GuC due to limitations
in how submission is implemented in run_job().

Also if all pagefault queues can skip the schedule disable during a
switch to dma-fence mode, do not schedule a resume for the pagefault
queues after the next submission.

v2:
 - Don't touch the LRC tail is queue is suspended but enabled in run_job
   (CI)

Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Link: https://patch.msgid.link/20251212182847.1683222-5-matthew.brost@intel.com