padlock.c: guard mbedtls_padlock_xcryptcbc by CIPHER_MODE_CBC

Signed-off-by: Yanray Wang <yanray.wang@arm.com>
diff --git a/library/padlock.c b/library/padlock.c
index 563d40e..0ea4129 100644
--- a/library/padlock.c
+++ b/library/padlock.c
@@ -108,6 +108,7 @@
     return 0;
 }
 
+#if defined(MBEDTLS_CIPHER_MODE_CBC)
 /*
  * PadLock AES-CBC buffer en(de)cryption
  */
@@ -161,6 +162,7 @@
 
     return 0;
 }
+#endif /* MBEDTLS_CIPHER_MODE_CBC */
 
 #endif /* MBEDTLS_VIA_PADLOCK_HAVE_CODE */