parisc: Allow to reboot machine after system halt

commit 2028315c upstream.

In case a machine can't power-off itself on system shutdown,
allow the user to reboot it by pressing the RETURN key.

Cc: <stable@vger.kernel.org> # v4.14+
Signed-off-by: Helge Deller <deller@gmx.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>