iwl3945: Getting rid of iwl-3945-debug.h

At the cost of adding a debug_level field to iwl3945_priv, we are now able to
get rid of iwl-3945-debug.h, and use iwl-debug.h instead.

Signed-off-by: Samuel Ortiz <samuel.ortiz@intel.com>
Signed-off-by: Abhijeet Kolekar <abhijeet.kolekar@intel.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>