drm/xe/svm: Fix regression disallowing 64K SVM migration

When changing the condition from >= SZ_64K, it was changed to <= SZ_64K.
This disallows migration of 64K, which is the exact minimum allowed.

Closes: https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/5057


Fixes: a9ac0fa4 ("drm/xe: Strict migration policy for atomic SVM faults")
Cc: stable@vger.kernel.org
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>
Reviewed-by: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>
Signed-off-by: Maarten Lankhorst <dev@lankhorst.se>
Link: https://lore.kernel.org/r/20250521090102.2965100-1-dev@lankhorst.se