RADIUS: Allow RADIUS server to provide PSK instead of passphrase

RADIUS: Allow RADIUS server to provide PSK instead of passphrase

If the AP is slow, passphrase hashing takes too long to serve the client
before timeout. Extend the Tunnel-Password design to allow a 64
character value to be interpreted as a PSK and send SSID to RADIUS
server. This allows the RADIUS server to either take care of passphrase
hashing or to use raw PSK without such hashing.

This is especially important for FT-PSK with FT-over-air, where hashing
cannot be deferred.

Signed-off-by: Michael Braun <michael-dev@fami-braun.de>