drm/xe/guc: Split g2h worker function

In the next patch we will want to perform the same steps that
g2h worker function is doing but from the different worker.

Suggested-by: Matthew Brost <matthew.brost@intel.com>
Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240606130639.1504-2-michal.wajdeczko@intel.com