Fix missing preprocessor condition in AES self-test
The AES OFB self-test made use of a variable `offset` but failed to have a
preprocessor condition around it, so unless CTR and CBC were enabled, the
variable would be undeclared.
@@ -1397,7 +1397,8 @@ int mbedtls_aes_self_test( int verbose )
#if defined(MBEDTLS_CIPHER_MODE_CBC)
unsigned char prv[16];
#endif
-#if defined(MBEDTLS_CIPHER_MODE_CTR) || defined(MBEDTLS_CIPHER_MODE_CFB)
+#if defined(MBEDTLS_CIPHER_MODE_CTR) || defined(MBEDTLS_CIPHER_MODE_CFB) || \
+ defined(MBEDTLS_CIPHER_MODE_OFB)
size_t offset;
#endif
#if defined(MBEDTLS_CIPHER_MODE_CTR)
