iwlwifi: remove most of the iwl_priv references from iwl-ucode.c

Remove all but the last few references to iwl_priv from the lower
level iwl-ucode.c, with resulting code changes.

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