mac80211: adding 802.11n HT framework definitions

New structures:
 - ieee80211_ht_info: describing STA's HT capabilities
 - ieee80211_ht_bss_info: describing BSS's HT characteristics
Changed structures:
 - ieee80211_hw_mode: now also holds PHY HT capabilities for each HW mode
 - ieee80211_conf: ht_conf holds current self HT configuration
                   ht_bss_conf holds current BSS HT configuration
 - flag IEEE80211_CONF_SUPPORT_HT_MODE added to indicate if HT use is
   desired
 - sta_info: now also holds Peer's HT capabilities

Signed-off-by: Ron Rindjunsky <ron.rindjunsky@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>