drm/xe: Allow freeing of a managed bo

If a bo is created via xe_managed_bo_create_pin_map() then it cannot be
freed by the driver using xe_bo_unpin_map_no_vm(), or indeed any other
existing function. The DRM layer will still have a pointer stashed
away for later freeing, causing a invalid memory access on driver
unload. So add a helper for releasing the DRM action as well.

v2: Drop 'xe' parameter (review feedbak from Michal W)

Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
Reviewed-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Link: https://lore.kernel.org/r/20250910210237.603576-4-John.C.Harrison@Intel.com