iwlwifi: store ucode version number

We store the ucode version number as part of
iwl_priv/iwl3945_priv. This enables us to determine
if particular ucode has support for features in order
to have driver support more than one ucode API.

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