ARM: CPU hotplug: fix reporting of spurious wakeups

The original scheme for reporting spurious wakeups was broken - it
tried to use printk() from a context which wasn't coherent with the
other CPUs, which risks corrupting the printk() data.

Fix this by noting the number spurious wakeups, and only report them
when we are properly woken - when we will be coherent with the rest
of the system.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>