mac80211: replace SMPS hw flags with wiphy feature bits

Use the new static_smps / dynamic_smps feature bits
instead of mac80211-internal hw flags.

Signed-off-by: Eliad Peller <eliad@wizery.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>