iwlagn: fix priv->cfg->ht_params NULL pointer dereference

This fix regression introduced by commit:

commit 15b3f3b006b42a678523cad989bfd60b76bf4403
Author: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Date:   Fri Jun 3 07:54:13 2011 -0700

    iwlagn: set smps mode after assoc for 1000 device

Also remove unneeded brackets on the way.

Address:
https://bugzilla.redhat.com/show_bug.cgi?id=744155

Cc: stable@kernel.org # 3.1+
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>