mac80211: change MIMO_PS to SM_PS

This patch follows 11n spec naming more rigorously replacing MIMO_PS
with SM_PS (Spatial Multiplexing Power Save).

(Originally submitted as 4 patches, "mac80211: change MIMO_PS to SM_PS",
"iwlwifi: change MIMO_PS to SM_PS", "ath9k: change MIMO_PS to SM_PS",
and "iwlwifi: remove double definition of SM PS". -- JWL)

Signed-off-by: Ron Rindjunsky <ron.rindjunsky@intel.com>
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Zhu Yi <yi.zhu@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>