iwlwifi: replace iwl_priv reference with iwl_trans for ucode.

Replace the references to the iwl_priv structure with the iwl_trans
structure as the priv structure is never referenced other than to
access the trans structure.  Rename from iwlagn to iwl.

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>