perf tools: Centralize default columns init in perf_hpp__init

perf tools: Centralize default columns init in perf_hpp__init

Now when diff command is separated from other standard outputs,
we can use perf_hpp__init to initialize all standard columns.

Moving PERF_HPP__OVERHEAD column init back to perf_hpp__init,
and removing extra enable calls.

Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Reviewed-by: Namhyung Kim <namhyung@kernel.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-nj2xk89tj972tbqswfs498ex@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>