HT: Remove SMPS in AP mode

HT: Remove SMPS in AP mode

SM Power Save was described in somewhat unclear manner in IEEE Std
802.11n-2009 as far the use of it locally in an AP to save power. That
was clarified in IEEE Std 802.11-2016 to allow only a non-AP STA to use
SMPS while the AP is required to support an associated STA doing so. The
AP itself cannot use SMPS locally and the HT Capability advertisement
for this is not appropriate.

Remove the parts of SMPS support that involve the AP using it locally.
In practice, this reverts the following commits:
04ee647d58a2 ("HT: Let the driver advertise its supported SMPS modes for AP mode")
8f461b50cfe4 ("HT: Pass the smps_mode in AP parameters")
da1080d7215f ("nl80211: Advertise and configure SMPS modes")

Signed-off-by: Jouni Malinen <j@w1.fi>