intel_idle: Don't overreact to a cpuidle registration failure.

The helper function, intel_idle_cpu_init, registers one new device
with the cpuidle layer.  If the registration should fail, that
function immediately calls intel_idle_cpuidle_devices_uninit() to
unregister every last CPU's device.  However, it makes no sense to do
so, when called from the hot plug notifier callback.

This patch moves the call to intel_idle_cpuidle_devices_uninit()
outside of the helper function to the one call site that actually
needs to perform the de-registrations.

Signed-off-by: Richard Cochran <rcochran@linutronix.de>
Signed-off-by: Len Brown <len.brown@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>