drm/xe/vf: Shifting GGTT area post migration

drm/xe/vf: Shifting GGTT area post migration

We have only one GGTT for all IOV functions, with each VF having assigned
a range of addresses for its use. After migration, a VF can receive a
different range of addresses than it had initially.

This implements shifting GGTT addresses within drm_mm nodes, so that
VMAs stay valid after migration. This will make the driver use new
addresses when accessing GGTT from the moment the shifting ends.

By taking the ggtt->lock for the period of VMA fixups, this change
also adds constraint on that mutex. Any locks used during the recovery
cannot ever wait for hardware response - because after migration,
the hardware will not do anything until fixups are finished.

v2: Moved some functs to xe_ggtt.c; moved shift computation to just
  after querying; improved documentation; switched some warns to asserts;
  skipping fixups when GGTT shift eq 0; iterating through tiles (Michal)
v3: Updated kerneldocs, removed unused funct, properly allocate
  balloning nodes if non existent
v4: Re-used ballooning functions from VF init, used bool in place of
  standard error codes
v5: Renamed one function
v6: Subject tag change, several kerneldocs updated, some functions
  renamed, some moved, added several asserts, shuffled declarations
  of variables, revealed more detail in high level functions
v7: Fixed typos, added `_locked` suffix to some functs, improved
  readability of asserts, removed unneeded conditional
v8: Moved one function, removed implementation detail from kerneldoc,
  added asserts
v9: Code shuffling without much change, and one param rename
v10: Minor error path change, added printing the shift via debugfs

Signed-off-by: Tomasz Lis <tomasz.lis@intel.com>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Reviewed-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Link: https://lore.kernel.org/r/20250512114018.361843-3-tomasz.lis@intel.com