tools headers UAPI: update linux/in.h copy

To get the changes from:

  645f0897 ("net: Fix some comments")

That don't cause any changes in tooling, its just a typo fix.

This silences this tools/perf build warning:

  Warning: Kernel ABI header at 'tools/include/uapi/linux/in.h' differs from latest version at 'include/uapi/linux/in.h'
  diff -u tools/include/uapi/linux/in.h include/uapi/linux/in.h

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>