Soon we will be trying to communicate with the GuC firmware very
early during VF driver probe, before we finish normal init steps.
Split GuC communication initialization code so the GuC MMIO based
communication xe_guc_mmio_send() functions will work where needed.

Cc: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Link: https://lore.kernel.org/r/20240111162051.585-1-michal.wajdeczko@intel.comSigned-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>