hostapd: enable SHA256-based algorithms

Enable support for stronger SHA256-based algorithms in hostapd and
wpa_supplicant when using WPA-EAP or WPA-PSK with 802.11w enabled.

We cannot unconditionally enable it, as it requires hostapd to be
compiled with 802.11w support, which is disabled in the -mini variants.

Signed-off-by: Stijn Tintel <stijn@linux-ipv6.be>
Tested-by: Sebastian Kemper <sebastian_ml@gmx.net>