mac80211: HE: set RX NSS

In case of HE, the RX NSS is taken from the HE capabilities.
If the supported NSS capabilities that are reported by AP for
HE mode in the HE Capabilities element are different from the NSS
capabilities that are reported by AP for the VHT mode in the VHT
Capabilities element, use the lowest supported NSS to not get all
the values confused.

Signed-off-by: Tova Mussai <tova.mussai@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Link: https://lore.kernel.org/r/20200131111300.891737-9-luca@coelho.fi


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