iwlwifi: generalize iwlwifi init flow

This patch creates handlers to support
iwlwifi init flow for multiple HWs

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