perf tools: Fix syscalltbl build failure

perf tools: Fix syscalltbl build failure

The build of kernel v4.14-rc1 for i686 fails on RHEL 6 with the error
in tools/perf:

  util/syscalltbl.c:157: error: expected ';', ',' or ')' before '__maybe_unused'
  mv: cannot stat `util/.syscalltbl.o.tmp': No such file or directory

Fix it by placing/moving:

  #include <linux/compiler.h>

  outside of #ifdef HAVE_SYSCALL_TABLE block.

Signed-off-by: Akemi Yagi <toracat@elrepo.org>
Cc: Alan Bartlett <ajb@elrepo.org>
Link: http://lkml.kernel.org/r/oq41r8$1v9$1@blaine.gmane.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>