[POWERPC] PowerPC 440EPx: Sequoia board support

AMCC PPC440EPx Sequoia board support.

Signed-off-by: Valentine Barshak <vbarshak@ru.mvista.com>
Acked-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Josh Boyer <jwboyer@linux.vnet.ibm.com>