drm/i915/psr: Add interface to check if AUXLess ALPM is needed by PSR

Currently we spread ugly PSR details into ALPM code to check if AUXLess
ALPM is needed. Prepare to hide these details to PSR code by adding new
interface for checking if AUXLess ALPM is needed.

v2: remove kerneldoc comment

Signed-off-by: Jouni Högander <jouni.hogander@intel.com>
Reviewed-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Link: https://lore.kernel.org/r/20250526120512.1702815-7-jouni.hogander@intel.com