drm/xe: Opportunistically skip TLB invalidaion on unbind

drm/xe: Opportunistically skip TLB invalidaion on unbind

If a range or VMA is invalidated and scratch page is disabled, there
is no reason to issue a TLB invalidation on unbind, skip TLB
innvalidation is this condition is true. This is an opportunistic check
as it is done without the notifier lock, thus it possible for the range
to be invalidated after this check is performed.

This should improve performance of the SVM garbage collector, for
example, xe_exec_system_allocator --r many-stride-new-prefetch, went
~20s to ~9.5s on a BMG.

v2:
 - Use helper for valid check (Thomas)
v3:
 - Avoid skipping TLB invalidation if PTEs are removed at a higher
   level than the range
 - Never skip TLB invalidations for VMA
 - Drop Himal's RB

Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>
Link: https://lore.kernel.org/r/20250616063024.2059829-3-matthew.brost@intel.com