openssl: fix potential size overflow when writing data

Our `openssl_write` function calls `SSL_write` by passing in both `data`
and `len` arguments directly. Thing is, our `len` parameter is of type
`size_t` and theirs is of type `int`. We thus need to clamp our length
to be at most `INT_MAX`.

src/streams/openssl.c

@@ -649,9 +649,8 @@ static ssize_t openssl_write(git_stream *stream, const char *data, size_t data_l
 
 	GIT_UNUSED(flags);
 
-	if ((ret = SSL_write(st->ssl, data, len)) <= 0) {
+	if ((ret = SSL_write(st->ssl, data, len)) <= 0)
 		return ssl_set_error(st->ssl, ret);
-	}
 
 	return ret;
 }