drm/xe/vf: Start CTs before resfix VF post migration recovery

drm/xe/vf: Start CTs before resfix VF post migration recovery

Before RESFIX_DONE, all CTs stuck in the H2G queue need to be squashed,
as they may contain actions which contain invalid GGTT references or are
unnecessary after HW change.

Starting the CTs clears all H2Gs in the queue. Any lost H2Gs are
resubmitted by the GuC submission state machine.

v3:
 - Don't mess with head / tail values (Michal)
v4:
 - Don't mess with broke (Michal)
 - Add CTB_H2G_BUFFER_OFFSET (Michal)
v5:
 - Adjust commit message (Tomasz)

Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Link: https://lore.kernel.org/r/20251008214532.3442967-25-matthew.brost@intel.com