drm/xe: Assert that VF will never use fixed placement of BOs

drm/xe: Assert that VF will never use fixed placement of BOs

Most BOs do not care at which offset they will be accessed within
GGTT or PPGTT. The few which do care, should be only created
on PF, and mapped within GGTT. On VFs, mapping at fixed offset
is prohibited, as each VF is granted access to a range of
GGTT address space.

Since fixed addresses of GGTT mapping can only be used on PF,
add an assert which makes sure no attempt of fixed placement
will happen for a driver probed on a VF.

Reviewed-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Signed-off-by: Tomasz Lis <tomasz.lis@intel.com>
Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Link: https://lore.kernel.org/r/20251021224817.1593817-4-tomasz.lis@intel.com