iwlagn: default smps mode for 1000 series device

1000 series are 1x2 devices, the old default using static smps which only
use single antenna for rx, set the default to dynamic smps.

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