PSK PRF correction.
PSK PRF correction.

For SHA384 PRF PSK ciphersuites we have to switch to default PRF for
TLS < 1.2

Reviewed-by: Matt Caswell <1fa2ef4755a9226cb9a0a4840bd89b158ac71391@openssl.org>

openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl