For whatever reason, serial output is really slow on P550, to
the point where drawing the grub menu takes an annoyingly long
amount of time and really gets in the way.
To avoid that issue, use the countdown timeout instead. This
still gives users a chance to enter the full menu if they need
to while making things a lot faster for regular boots.
Signed-off-by: Andrea Bolognani <abologna@redhat.com>
63f51b6207