dh_client: removed under CIPHER_ENCRYPT_ONLY

dh_client requests AES-ECB to do decryption. So it needs to be
removed under CIPHER_ENCRYPT_ONLY.

Signed-off-by: Yanray Wang <yanray.wang@arm.com>
diff --git a/programs/pkey/dh_client.c b/programs/pkey/dh_client.c
index 5a2c30f..9dd38bc 100644
--- a/programs/pkey/dh_client.c
+++ b/programs/pkey/dh_client.c
@@ -56,6 +56,13 @@
                    "MBEDTLS_CTR_DRBG_C and/or MBEDTLS_SHA1_C not defined.\n");
     mbedtls_exit(0);
 }
+
+#elif defined(MBEDTLS_CIPHER_ENCRYPT_ONLY)
+int main(void)
+{
+    mbedtls_printf("MBEDTLS_CIPHER_ENCRYPT_ONLY implicitly defined.\n");
+    mbedtls_exit(0);
+}
 #else