drm/xe: Separate early xe_device initialization

drm/xe: Separate early xe_device initialization

We would like to initialize more of the xe_device struct also from
the kunit code, as it should be safe to use most of the generic drm
or xe components without doing any additional tweaks. Separate early
xe initialization code to a new function, so it can be reused.

Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Reviewed-by: Raag Jadav <raag.jadav@intel.com>
Reviewed-by: Gustavo Sousa <gustavo.sousa@intel.com>
Link: https://patch.msgid.link/20260526195452.20545-6-michal.wajdeczko@intel.com