mac80211: minstrel_ht: fix a logic error in RTS/CTS handling

mac80211: minstrel_ht: fix a logic error in RTS/CTS handling

BugLink: http://bugs.launchpad.net/bugs/1558330
commit c36dd3eaf1a674a45b58b922258d6eaa8932e292 upstream.

RTS/CTS needs to be enabled if the rate is a fallback rate *or* if it's
a dual-stream rate and the sta is in dynamic SMPS mode.

Fixes: a3ebb4e1b763 ("mac80211: minstrel_ht: handle peers in dynamic SMPS")
Reported-by: Matías Richart <mrichart@fing.edu.uy>
Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>