perf tools: Add missing linux/compiler.h include to perf-sys.h

It uses the likely/unlikely macros, so need to include
<linux/compiler.h>.

Cc: Adrian Hunter <adrian.hunter@intel.com>
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-p0xrhgbkicsii9ohmhhprqpi@git.kernel.org


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>