arm64: dts: NS2 secondary core enablement via PSCI

Declare PSCI-1.0 node and enable CPU_ON method via PSCI.  Spin-table
memreserve has been removed as well as syscon based reset, as PSCI-1.0
expects reset implementation in firmware.

Signed-off-by: Luke Starrett <luke.starrett@broadcom.com>
Acked-by: Scott Branden <scott.branden@broadcom.com>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>