ice: Change ice_info_get_dsn to be void

ice_info_get_dsn always returns 0, so just make it void.

Signed-off-by: Anirudh Venkataramanan <anirudh.venkataramanan@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>