perf report: Make dso__calc_col_width agree with hist_entry__dso_snprintf

The first was always using the ->long_name, while the later used
->short_name if verbose was not set, resulting in the dso column to be
much wider than needed most of the time.

Cc: Frédéric Weisbecker <fweisbec@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Tom Zanussi <tzanussi@gmail.com>
LKML-Reference: <new-submission>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>