drm/xe: Invalidate TLB also on bind if in scratch page mode

For scratch table mode we need to cover the case where a scratch PTE might
have been pre-fetched and cached and used instead of that of the newly
bound vma.
For compute vms, invalidate TLB globally using GuC before signalling
bind complete. For !long-running vms, invalidate TLB at batch start.

Also document how TLB invalidation works.

v2:
- Fix a pointer to the comment about TLB invalidation (Jose Souza).
- Add a bool to the vm whether we want to invalidate TLB at batch start.
- Invalidate TLB also on BCS- and video engines at batch start where
  needed.
- Use BIT() macro instead of explicit shift.

Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Tested-by: José Roberto de Souza <jose.souza@intel.com> #v1
Reported-by: José Roberto de Souza <jose.souza@intel.com> #v1
Link: #291
Closes: #291


Acked-by: José Roberto de Souza <jose.souza@intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>