Fix server mode only build of v3.6 with MBEDTLS_SSL_CLI_C unset (fixes #9186)

Signed-off-by: Michael Schuster <michael@schuster.ms>
diff --git a/library/ssl_misc.h b/library/ssl_misc.h
index a8807f6..8402fe8 100644
--- a/library/ssl_misc.h
+++ b/library/ssl_misc.h
@@ -1507,7 +1507,7 @@
 #endif /* MBEDTLS_KEY_EXCHANGE_SOME_PSK_ENABLED */
 
 #if defined(MBEDTLS_SSL_HANDSHAKE_WITH_PSK_ENABLED)
-#if defined(MBEDTLS_SSL_CLI_C)
+#if defined(MBEDTLS_SSL_CLI_C) || defined(MBEDTLS_SSL_SRV_C)
 MBEDTLS_CHECK_RETURN_CRITICAL
 int mbedtls_ssl_conf_has_static_psk(mbedtls_ssl_config const *conf);
 #endif