perf hists: Fix period symbol_conf.field_sep display

perf hists: Fix period symbol_conf.field_sep display

Currently we don't properly display hist data with symbol_conf.field_sep
separator. We need to display either space or separator.

Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: http://lkml.kernel.org/n/tip-cyggwys0bz5kqdowwvfd8h72@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>