drm/xe/vf: Use drm mm instead of drm sa for CCS read/write

drm/xe/vf: Use drm mm instead of drm sa for CCS read/write

The suballocator algorithm tracks a hole cursor at the last allocation
and tries to allocate after it. This is optimized for fence-ordered
progress, where older allocations are expected to become reusable first.

In fence-enabled mode, that ordering assumption holds. In fence-disabled
mode, allocations may be freed in arbitrary order, so limiting allocation
to the current hole window can miss valid free space and fail allocations
despite sufficient total space.

Use DRM memory manager instead of sub-allocator to get rid of this issue
as CCS read/write operations do not use fences.

Fixes: 864690cf4dd6 ("drm/xe/vf: Attach and detach CCS copy commands with BO")
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/20260408110145.1639937-6-satyanarayana.k.v.p@intel.com