Use same type for ids everywhere.

In case of writing to perf.data the size is u32. In pipe mode it is
limited to header.size (less than u16). Adding a size check here.

Size overflow due to casting shouldn't actually happen in practice, but
during development this may cause type missmatch warninngs/errors,
unifying types avoids this.
Signed-off-by: NRobert Richter <robert.richter@amd.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1345144224-27280-2-git-send-email-robert.richter@amd.comSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>