mac80211: support S1G STA capabilities

Include the S1G Capabilities element in an association
request, and support the cfg80211 capability overrides.

Signed-off-by: Thomas Pedersen <thomas@adapt-ip.com>
Link: https://lore.kernel.org/r/20200922022818.15855-5-thomas@adapt-ip.com
[pass skb to ieee80211_add_s1g_capab_ie(), small code style edits]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>