Allow ECB mode in cryptsetup benchmark.

TODO

@@ -4,7 +4,6 @@ Version 1.7:
 - TRIM for keyslots
 - Do we need crypt_data_path() - path to data device (if differs)?
 - Resync ETA time is not accurate, calculate it better (last minute window?).
-- Crypt benchmark cannot test ECB mode.
 - crypto backend should initialise itself only once (debug log)
 - Extend existing LUKS header to use another KDF? (https://password-hashing.net/)
 - Fix all crazy automake warnings (or switch to Cmake).

src/cryptsetup.c

@@ -540,6 +540,9 @@ static int action_benchmark(void)
 		    strstr(cipher, "cast5"))
 			iv_size = 8;
 
+		if (!strcmp(cipher_mode, "ecb"))
+			iv_size = 0;
+
 		r = benchmark_cipher_loop(cipher, cipher_mode,
 					  key_size / 8, iv_size,
 					  &enc_mbr, &dec_mbr);