tools include uapi: Grab a copy of linux/kcmp.h

tools include uapi: Grab a copy of linux/kcmp.h

We will use it to generate tables for beautifying kcmp's 'type' arg.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andrey Vagin <avagin@openvz.org>
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-r35zr79invmpinfe1zu57cas@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>