iwlagn: move ucode files out of the iwl_priv structure

Relocate the ucode files and update relevant code.
More code refactoring.

Signed-off-by: Don Fry <donald.h.fry@intel.com>
Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>