Replace MBEDTLS_KEY_EXCHANGE_PSK_ENABLED with MBEDTLS_KEY_EXCHANGE_SOME_NON_PFS_ENABLED

Signed-off-by: Ben Taylor <ben.taylor@linaro.org>
diff --git a/include/mbedtls/ssl_ciphersuites.h b/include/mbedtls/ssl_ciphersuites.h
index 48e77d1..05cd666 100644
--- a/include/mbedtls/ssl_ciphersuites.h
+++ b/include/mbedtls/ssl_ciphersuites.h
@@ -185,7 +185,7 @@
 #endif
 
 /* Key exchanges that don't involve ephemeral keys */
-#if defined(MBEDTLS_KEY_EXCHANGE_PSK_ENABLED)
+#if defined(MBEDTLS_KEY_EXCHANGE_SOME_NON_PFS_ENABLED)
 #define MBEDTLS_KEY_EXCHANGE_SOME_NON_PFS_ENABLED
 #endif