ARM: TC2: reset CPUs spuriously woken up on cluster power up

ARM: TC2: reset CPUs spuriously woken up on cluster power up

On TC2, all CPUs in a cluster are woken up when an IRQ event triggers for a
CPU in a cluster in shutdown state.

This patch puts spuriously woken CPUs back in reset by checking the
pending IRQ status in the SPC wake-up interrupt status register; if the
CPU has no pending IRQ routed to it, the core reexecutes wfi and it is put
in reset by FW straight away.

Tested-by: Viresh Kumar <viresh.kumar2@arm.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>