mac80211: save transmit power envelope element and power constraint

This is to save the transmit power envelope element and power
constraint in struct ieee80211_bss_conf for 6 GHz. Lower driver
will use this info to calculate the power limit.

Signed-off-by: Wen Gong <wgong@codeaurora.org>
Link: https://lore.kernel.org/r/20210924100052.32029-7-wgong@codeaurora.org


Signed-off-by: Johannes Berg <johannes.berg@intel.com>