iwlwifi: add iwl_hw_detect function to iwl core

This patch add iwl_hw_detect function to iwl core

Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>