perf arm-spe: Use advertised caps/min_interval as default sample_period

When recording SPE traces, the default sample_period is currently being
set to 1 in the perf_event_attr fields, instead of the value advertised
in '/sys/devices/arm_spe_0/caps/min_interval':

Before:

  $ perf record -e arm_spe// -vv -- sleep 1
  [...]
    { sample_period, sample_freq }   1
  [...]

Use the value from the above sysfs location as a more sensible default
(it was already being read, but the value not being used)

After:

  $ perf record -e arm_spe// -vv -- sleep 1
  [...]
    { sample_period, sample_freq }   1024
  [...]

Reviewed-by: Leo Yan <leo.yan@linaro.org>
Signed-off-by: German Gomez <german.gomez@arm.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: John Garry <john.garry@huawei.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Will Deacon <will@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org
Link: https://lore.kernel.org/r/20220221171042.58460-1-german.gomez@arm.com


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>