Allow user to disable HE mode, similar to how VHT and HT
can be disabled.  Useful for testing.
Signed-off-by: NBen Greear <greearb@candelatech.com>
Link: https://lore.kernel.org/r/20210204144610.25971-1-greearb@candelatech.comSigned-off-by: NJohannes Berg <johannes.berg@intel.com>