Move it out of the xe_migrate compilation unit so it can be re-used in
other places.

Cc: Matthew Brost <matthew.brost@intel.com>
Signed-off-by: Francois Dugast <francois.dugast@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240614094433.775866-1-francois.dugast@intel.comSigned-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>