Fix itinerate struct beep array

[guy fleury iteriteka]

Hello,

http://git.savannah.gnu.org/cgit/hurd/hurd.git/tree/console-client/generic-speaker.c#n417

for (i = 0; i < sizeof (*beep); i++)
should be:
for (i = 0; i < (sizeof(beep) / sizeof (*beep)); i++)

I don't have a hurd vm right now to send patch.