[POWERPC] booting-without-of: localbus should not include board name

Fix documentation once and for ever, because I'm pretty tired of
repeating that I am merely following it. ;-)

http://ozlabs.org/pipermail/linuxppc-dev/2007-December/048096.html

http://ozlabs.org/pipermail/linuxppc-dev/2007-November/046977.html
http://ozlabs.org/pipermail/linuxppc-dev/2007-November/046979.html

http://ozlabs.org/pipermail/linuxppc-dev/2007-October/044411.html
http://ozlabs.org/pipermail/linuxppc-dev/2007-October/044413.html

Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>