Uses the arch/x86/ kernel code for x86_64/i386, fallbacking to a gcc
intrinsics implementation that has been tested in at least sparc64.
Will be used for reference counting in tools/perf.
Acked-by: David Ahern
Cc: Adrian Hunter
Cc: Borislav Petkov
Cc: Don Zickus
Cc: Frederic Weisbecker
Cc: Jiri Olsa
Cc: Namhyung Kim
Cc: Peter Zijlstra
Cc: Stephane Eranian
Link: http://lkml.kernel.org/n/tip-knfpjowhgyh6x4z0kfuk389j@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo