drm/xe: Convert xe_dma_buf.c for exhaustive eviction

Convert dma-buf migration to XE_PL_TT and dma-buf import to
support exhaustive eviction, using xe_validation_guard().
It seems unlikely that the import would result in an -ENOMEM,
but convert import anyway for completeness.

The dma-buf map_attachment() functionality unfortunately doesn't
support passing a drm_exec, which means that foreign devices
validating a dma-buf that we exported will not, unless they are
xeKMD devices, participate in the exhaustive eviction scheme.

v2:
- Avoid gotos from within xe_validation_guard(). (Matt Brost)
- Adapt to signature change of xe_validation_guard(). (Matt Brost)
- Remove an unneeded (void)ret. (Matt Brost)
- Fix up an error path.

Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Link: https://lore.kernel.org/r/20250908101246.65025-9-thomas.hellstrom@linux.intel.com