iwlwifi: remove unneeded __packed

struct iwl_queue is not part of firmware interface, so __packed is not
needed. Remove it since is may affect performance.

Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Acked-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>