x86/platform: Remove warning message for duplicate NMI handlers

Remove the WARNING message associated with multiple NMI handlers as
there are at least two that are legitimate.  These are the KGDB and the
UV handlers and both want to be called if the NMI has not been claimed
by any other NMI handler.

Use of the UNKNOWN NMI call chain dramatically lowers the NMI call rate
when high frequency NMI tools are in use, notably the perf tools.  It is
required on systems that cannot sustain a high NMI call rate without
adversely affecting the system operation.

Signed-off-by: Mike Travis <mike.travis@hpe.com>
Reviewed-by: Dimitri Sivanich <dimitri.sivanich@hpe.com>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Russ Anderson <russ.anderson@hpe.com>
Cc: Frank Ramsay <frank.ramsay@hpe.com>
Cc: Tony Ernst <tony.ernst@hpe.com>
Link: http://lkml.kernel.org/r/20170307210841.730959611@asylum.americas.sgi.com


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