drm/xe: Add memory pool with shadow support

drm/xe: Add memory pool with shadow support

Add a memory pool to allocate sub-ranges from a BO-backed pool
using drm_mm.

Signed-off-by: Satyanarayana K V P <satyanarayana.k.v.p@intel.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Maarten Lankhorst <dev@lankhorst.se>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Link: https://patch.msgid.link/20260408110145.1639937-5-satyanarayana.k.v.p@intel.com