drm/xe: Wait for migration job before unmapping pages

drm/xe: Wait for migration job before unmapping pages

Fix a potential GPU page fault during tt -> system moves by waiting for
migration jobs to complete before unmapping SG. This ensures that IOMMU
mappings are not prematurely torn down while a migration job is still in
progress.

v2: Use intr=false(Matt A)
v3: Update commit message(Matt A)
v4: s/DMA_RESV_USAGE_BOOKKEEP/DMA_RESV_USAGE_KERNEL(Thomas)

Closes: https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/3466
Fixes: 75521e8b56e8 ("drm/xe: Perform dma_map when moving system buffer objects to TT")
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Cc: stable@vger.kernel.org # v6.11+
Cc: Matthew Auld <matthew.auld@intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Reviewed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241213122415.3880017-2-nirmoy.das@intel.com
Signed-off-by: Nirmoy Das <nirmoy.das@intel.com>