drm/xe/sriov: support non-contig VRAM provisioning

Currently we can run into issues with provisioning VRAM region, due to
requiring contig VRAM BO underneath. We sometimes see that allocation
(multiple GB) can fail even when there is enough free space.  We don't
need CPU access to the buffer in the first place, so can forgo pin_map
and therefore also the contig requirement. Keep the same behavior with
save and restore during suspend/resume (which can now be done with
blitter).  We also need the VRAM to occupy the same pages so we don't
need to re-program the LMTT, so should still remain pinned (also we
don't want something to try evict it). With that covert over to plain
pinned kernel object.

Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Satyanarayana K V P <satyanarayana.k.v.p@intel.com>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Satyanarayana K V P <satyanarayana.k.v.p@intel.com>
Link: https://lore.kernel.org/r/20250403102440.266113-16-matthew.auld@intel.com