perf evsel: Enable type checking for perf_evsel_config_term types

Use a typed enum for the perf_evsel_config_term type enum.  This allows
gcc to do much stronger type checks, and also check for missing case
statements.

I removed the unused _MAX member from the number.

It found one missing case. I'm not sure it's a real problem, so I just
turned it into a BUG_ON for now.

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Link: http://lkml.kernel.org/r/20171020202755.21410-1-andi@firstfloor.org


[ Renamed the enum name to term_type as per jolsa's request ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>