x86/mcheck: Move threshold_create_device()

Move the threshold_create_device() so it can use
threshold_remove_device() without a forward declaration.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Acked-by: Borislav Petkov <bp@alien8.de>
Cc: Tony Luck <tony.luck@intel.com>
Cc: rt@linutronix.de
Cc: linux-edac@vger.kernel.org
Link: http://lkml.kernel.org/r/20161110174447.11848-2-bigeasy@linutronix.de


Signed-off-by: Thomas Gleixner <tglx@linutronix.de>