When performing SAE authentication, connections and roaming to IoT APs
on the 2.4 GHz band were failing because the 6 Mbps rate was not set,
defaulting to the CCK rate instead.
This fix ensures that SAE authentication uses the 6 Mbps rate for both
initial connections and roaming on 2.4 GHz IoT APs.
Change-Id: I2ec57373c07584676ef9ecb049bc668fb7016d6a
CRs-Fixed: 3947657