iwlwifi: use iwl-commands.h also in 3945

This patch uses iwl-commands.h also for iwl3945
more clean ups are required but this get to stage where it
compiles cleanly.
Most massive changes are in spectrum and power managment.

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