Fix the issue that aes-xxx-siv algorithms failed in OpenSSL speed test

Speed test, aes-siv related cases fail on both x86 and arm.
The return value of siv_init() causes this problem, remove
the iv check to fix it.
Verify it locally, the result is pass.

Fixes #10416

Change-Id: If1a18599f3d0f56f22a1ce4f8f114b8db0f68cca
Reviewed-by: NRichard Levitte <levitte@openssl.org>
Reviewed-by: NShane Lontis <shane.lontis@oracle.com>
(Merged from https://github.com/openssl/openssl/pull/10419)

providers/implementations/ciphers/cipher_aes_siv.c

@@ -49,9 +49,6 @@ static int siv_init(void *vctx, const unsigned char *key, size_t keylen,
 
     ctx->enc = enc;
 
-    if (iv != NULL)
-        return 0;
-
     if (key != NULL) {
         if (keylen != ctx->keylen) {
             ERR_raise(ERR_LIB_PROV, PROV_R_INVALID_KEY_LENGTH);