iwlwifi: unify init driver flow

This patch does the following:
1 - moving init_drv from handler to regular function call
2 - move the init driver flow from iwl4965 to iwlcore, thus unify it to all
iwl family as a single flow
3 - move some general purpose functions from iwl4965 to iwlcore

Signed-off-by: Ron Rindjunsky <ron.rindjunsky@intel.com>
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>