perf tools: Fix column alignment when headers aren't shown on TUI

perf tools: Fix column alignment when headers aren't shown on TUI

If user sets ui.show-headers config option to false, it didn't calculate
default column width so it broke the alignment.  This is because it does
the calculation just before showing headers.

Move it to the beginning of the hist browser so that it can be called
regardless of the config option.

Reported-by: Jiri Olsa <jolsa@redhat.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung.kim@lge.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1406785662-5534-8-git-send-email-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>