powerpc/44x: Enable CRASH_DUMP for 440x

Now that we have relocatable kernel, supporting CRASH_DUMP only requires
turning the switches on for UP machines.

We don't have kexec support on 47x yet. Enabling SMP support would be done
as part of enabling the PPC_47x support.

Signed-off-by: Suzuki K. Poulose <suzuki@in.ibm.com>
Cc: Josh Boyer <jwboyer@gmail.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: linuxppc-dev <linuxppc-dev@lists.ozlabs.org>
Signed-off-by: Josh Boyer <jwboyer@gmail.com>