kvm tools: Use writev() in xwritev()

This patch fixes a typo in xwritev(). Luckily the function is not used so the
problem is only latent. Spotted during code review.

Cc: Sasha Levin <levinsasha928@gmail.com>
Signed-off-by: Pekka Enberg <penberg@kernel.org>

read-write.c

@@ -173,7 +173,7 @@ ssize_t xwritev(int fd, const struct iovec *iov, int iovcnt)
 	ssize_t nr;
 
 restart:
-	nr = write(fd, iov, iovcnt);
+	nr = writev(fd, iov, iovcnt);
 	if ((nr < 0) && ((errno == EAGAIN) || (errno == EINTR)))
 		goto restart;