drm/xe/uc: Extract xe_uc_sanitize_reset

Earlier GuC load will require more fine-grained control over reset.
Extract it outside of xe_uc_init_hw.

Signed-off-by: Michał Winiarski <michal.winiarski@intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>