85xx: Added support for multicore boot mechanism

Added the cpu command that provides a generic mechanism to get status,
reset, and release secondary cores in multicore processors.

Added support for using the ePAPR defined spin-table mechanism on 85xx.

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
Signed-off-by: Andy Fleming <afleming@freescale.com>