wifi: mac80211: add EHT MU-MIMO related flags in ieee80211_bss_conf

Similar to VHT/HE. This is utilized to pass MU-MIMO configurations
from user space (i.e. hostapd) to driver.

Signed-off-by: Ryder Lee <ryder.lee@mediatek.com>
Link: https://lore.kernel.org/r/8d9966c4c1e77cb1ade77d42bdc49905609192e9.1676628065.git.ryder.lee@mediatek.com


[move into combined if statement, reset on !eht]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>