perf stat: Add missing newline in pr_err messages

perf stat: Add missing newline in pr_err messages

The newline is missing for error messages in add_default_attributes()

Before:

  # perf stat --topdown
  Topdown requested but the topdown metric groups aren't present.
  (See perf list the metric groups have names like TopdownL1)#

After:

  # perf stat --topdown
  Topdown requested but the topdown metric groups aren't present.
  (See perf list the metric groups have names like TopdownL1)
  #

In addition, perf_stat_init_aggr_mode() and perf_stat_init_aggr_mode_file()
have the same problem, fixed by the way.

Signed-off-by: Yang Jihong <yangjihong1@huawei.com>
Acked-by: Ian Rogers <irogers@google.com>
Reviewed-by: James Clark <james.clark@arm.com>
Link: https://lore.kernel.org/r/20230614021505.59856-1-yangjihong1@huawei.com
Signed-off-by: Namhyung Kim <namhyung@kernel.org>