brcm63xx: hostapd.sh: set sae-mixed correctly

Seems for some reason when we set:
WPA-PSK-SHA256, then WPA-PSK don't work
correctly. Simple don't set this today.

Other mixed settings like:
wpa_key_mgmt=WPA-PSK FT-PSK SAE FT-SAE

root@iopsys:/# wl -i wl0 wpa_auth
0xc4080 WPA2-PSK FT SAE SAE-FT

works correctly.

Signed-off-by: Janusz Dziedzic <janusz.dziedzic@iopsys.eu>