iwlagn: fix null pointer access during ucode load on 1000

Commit "iwlwifi: Handle new firmware file with ucode build number
in header" introduced new ucode header parsing routines, but
neglected to initialize these routines for 1000. The system thus goes
into infinite loop trying to load ucode, failing every time with a null
pointer exception as it tries to parse the header.

Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Acked-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>