drm/xe/vf: Update pause/unpause() helpers with VF naming

drm/xe/vf: Update pause/unpause() helpers with VF naming

Now that pause/unpause() helpers have been updated for VF migration
usecase, update their naming to match the functionality and while at it,
add IS_SRIOV_VF() assert to make sure they are not abused.

v7: Add IS_SRIOV_VF() assert (Matthew Brost)
    Use "vf" suffix (Michal)

Suggested-by: Matthew Brost <matthew.brost@intel.com>
Signed-off-by: Raag Jadav <raag.jadav@intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Signed-off-by: Ashutosh Dixit <ashutosh.dixit@intel.com>
Link: https://patch.msgid.link/20251030122357.128825-2-raag.jadav@intel.com