[PATCH] documentation: Documentation/initrd.txt

I spent a long time the other day trying to examine an initrd image on a
fedora core 5 system because the initrd.txt file is apparently obsolete.
Here is a patch which I hope will reduce future confusion for others.

Signed-off-by: Thomas Horsley <tom.horsley@ccur.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>