Fix missing cipher mode dependencies

Signed-off-by: Andrzej Kurek <andrzej.kurek@arm.com>
diff --git a/tests/suites/test_suite_aes.function b/tests/suites/test_suite_aes.function
index 10e53c2..6a87d42 100644
--- a/tests/suites/test_suite_aes.function
+++ b/tests/suites/test_suite_aes.function
@@ -403,10 +403,14 @@
     defined(MBEDTLS_CIPHER_MODE_XTS) || \
     defined(MBEDTLS_CIPHER_MODE_CFB) || \
     defined(MBEDTLS_CIPHER_MODE_OFB)
-    mbedtls_aes_context aes_ctx;
     const unsigned char in[16] = { 0 };
     unsigned char out[16];
 #endif
+#if defined(MBEDTLS_CIPHER_MODE_CBC) || \
+    defined(MBEDTLS_CIPHER_MODE_CFB) || \
+    defined(MBEDTLS_CIPHER_MODE_OFB)
+mbedtls_aes_context aes_ctx;
+#endif
 #if defined(MBEDTLS_CIPHER_MODE_XTS)
     mbedtls_aes_xts_context xts_ctx;
 #endif