[PATCH] powerpc: Fix ppc32 initrd

OK, the Fedora ppc32 and ppc64 kernels should both be arch/powerpc by
tomorrow. They're booting on G5, POWER5, and my powerbook. I'll test
pmac SMP and Pegasos later -- but pmac smp is known broken in arch/ppc
anyway, and I'll live with a potential Pegasos regression for now; it
wasn't supported officially in FC4 either.

I needed to fix ppc32 initrd -- we were never setting initrd_start.

Signed-off-by: David Woodhouse <dwmw2@infradead.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>