arm64: dts: stratix10: Use PSCI node instead of spin-table for SMP

This reverts commit e6c041984533 ("FogBugz #491251: temporary remove
 PSCI node")
U-Boot has implemented PSCI which is preferable to the spin-table
so go back to using the PSCI node.

Signed-off-by: Dinh Nguyen <dinguyen@kernel.org>
Signed-off-by: Thor Thayer <thor.thayer@linux.intel.com>