drm/xe: Handle mixed mappings and existing VRAM on atomic faults

drm/xe: Handle mixed mappings and existing VRAM on atomic faults

Moving to VRAM will fail if mixed mappings are present or if the page is
already located in VRAM. Atomic faults that require a move to VRAM
currently retry without attempting to evict mixed mappings or locate
existing VRAM mappings.

This patch fixes the issue by attempting to evict mixed mappings or find
existing VRAM pages when a move to VRAM fails during atomic fault
handling.

Fixes: a9ac0fa455b0 ("drm/xe: Strict migration policy for atomic SVM faults")
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/20251009130629.3531962-1-matthew.brost@intel.com
(cherry picked from commit 75188605c56d10c1bd3b1cd94f4872f349c3a9c8)
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>