Fix compile-time guard in session cache implementation

Signed-off-by: Hanno Becker <hanno.becker@arm.com>
diff --git a/library/ssl_cache.c b/library/ssl_cache.c
index 1bbcc95..f337547 100644
--- a/library/ssl_cache.c
+++ b/library/ssl_cache.c
@@ -131,8 +131,9 @@
 {
 #if defined(MBEDTLS_HAVE_TIME)
     mbedtls_time_t t = mbedtls_time( NULL ), oldest = 0;
+#endif /* MBEDTLS_HAVE_TIME */
+
     mbedtls_ssl_cache_entry *old = NULL;
-#endif
     int count = 0;
     mbedtls_ssl_cache_entry *cur, *prv;