wifi: mac80211: fix probe req HE capabilities access

wifi: mac80211: fix probe req HE capabilities access

When building the probe request IEs HE support is checked for
the 6GHz band (wiphy->bands[NL80211_BAND_6GHZ]). If supported
the HE capability IE should be included according to the spec.
The problem is the 16-bit capability is obtained from the
band object (sband) that was passed in, not the 6GHz band
object (sband6). If the sband object doesn't support HE it will
result in a warning.

Fixes: 8bd862747463 ("mac80211: always include HE 6GHz capability in probe request")
Signed-off-by: James Prestwood <prestwoj@gmail.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>