Install the callbacks via the state machine and let the core invoke
the callbacks on the already online CPUs.

The smp_call_function_single() is dropped because the ONLINE callback is
invoked on the target CPU since commit 1cf4f629 ("cpu/hotplug: Move
online calls to hotplugged cpu"). smp_call_function_single() invokes the
invoked function with interrupts disabled, but this calling convention is
not preserved as the MSR is not modified by anything else than this code.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: linux-pci@vger.kernel.org
Cc: rt@linuxtronix.de
Link: http://lkml.kernel.org/r/20161117183541.8588-21-bigeasy@linutronix.deSigned-off-by: Thomas Gleixner <tglx@linutronix.de>