The (unsafe) function cpu_unlink_tb() is now unused, so we can simply
remove it and any code that was only used by it.
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: NRichard Henderson <rth@twiddle.net>
Signed-off-by: NBlue Swirl <blauwirbel@gmail.com>