[PATCH v6 0/8] Replace xe_hmm with gpusvm

[Matthew Auld <matthew.auld@intel.com>]

As a first step to moving userptr handling over to drm, replace the hmm
usage in xe over to gpusvm, which already offers similar functionality. As
some prep steps we also align on some of the missing pieces that were
already handled in xe_hmm.

v2:
  - Rework the gpusvm API based on feedback.
  - Unify SVM and userptr vm struct so we use the same notifier lock.
  - Drop the mark pages as dirty patch.
  - Various other improvements.
v3:
  - Further unify common handling of userptr and svm in xe.
v4:
  - Allow building xe without userptr, like when building on UML.
v5:
  - Rebase on lastest drm-tip. Lots of conflicts.
v6:
  - Various small fixes around kernel-doc etc.
  - Also convert over the newly added xe_vm_advise userptr usage.
-- 
2.51.0