drm/xe/uapi: Hide the madvise autoreset behind a VM_BIND flag

drm/xe/uapi: Hide the madvise autoreset behind a VM_BIND flag

The madvise implementation currently resets the SVM madvise if the
underlying CPU map is unmapped. This is in an attempt to mimic the
CPU madvise behaviour. However, it's not clear that this is a desired
behaviour since if the end app user relies on it for malloc()ed
objects or stack objects, it may not work as intended.

Instead of having the autoreset functionality being a direct
application-facing implicit UAPI, make the UMD explicitly choose
this behaviour if it wants to expose it by introducing
DRM_XE_VM_BIND_FLAG_MADVISE_AUTORESET, and add a semantics
description.

v2:
- Kerneldoc fixes. Fix a commit log message.

Fixes: a2eb8aec3ebe ("drm/xe: Reset VMA attributes to default in SVM garbage collector")
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>
Cc: "Falkowski, John" <john.falkowski@intel.com>
Cc: "Mrozek, Michal" <michal.mrozek@intel.com>
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Reviewed-by: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>
Link: https://lore.kernel.org/r/20251015170726.178685-2-thomas.hellstrom@linux.intel.com