tools: image-host.c: use correct variable for strerrno

In the function get_random_data, strerrno is called with
the variable ret (which is the return of the function
clock_gettime). It should be called with errnor. This
commit fixes this mistake.

Reported-by: Coverity (CID: 312956)
Signed-off-by: Philippe Reynes <philippe.reynes@softathome.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

tools/image-host.c

@@ -335,7 +335,7 @@ static int get_random_data(void *data, int size)
 	ret = clock_gettime(CLOCK_MONOTONIC, &date);
 	if (ret < 0) {
 		printf("%s: clock_gettime has failed (err=%d, str=%s)\n",
-		       __func__, ret, strerror(ret));
+		       __func__, ret, strerror(errno));
 		goto out;
 	}