perf tools: Check more combinations of PID/TID, UID and CPU switches

perf tools: Check more combinations of PID/TID, UID and CPU switches

There were some combinations of these switches that are not so
appropriate IMHO.

Since there are implicit priorities between them and they worked well
anyway, but it ends up opening useless duplicated events.

For example, 'perf stat -t <pid> -a' will open multiple events for the
thread instead of one.

Add explicit checks and warn user in perf_target__validate().

Signed-off-by: Namhyung Kim <namhyung.kim@lge.com>
Reviewed-by: David Ahern <dsahern@gmail.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1335417327-11796-7-git-send-email-namhyung.kim@lge.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>