perf arm-spe: Don't warn about the discard bit if it doesn't exist

perf arm-spe: Don't warn about the discard bit if it doesn't exist

Opening an SPE event shows a warning that doesn't concern the user:

  $ perf record -e arm_spe
  Unknown/empty format name: discard

Perf only wants to know if the discard bit is set for configuring the
event, not in response to anything the user has done. Fix it by adding
another helper that returns if a config bit exists without warning.

We should probably keep the warning in evsel__get_config_val() to avoid
having every caller having to do it, and most format bits should never
be missing.

Add a test for the new helper. Rename the parent test function to be
more generic rather than adding a new one as it requires a lot of
boilerplate.

Reviewed-by: Ian Rogers <irogers@google.com>
Reviewed-by: Leo Yan <leo.yan@arm.com>
Signed-off-by: James Clark <james.clark@linaro.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: John Garry <john.g.garry@oracle.com>
Cc: Leo Yan <leo.yan@linux.dev>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mike Leach <mike.leach@linaro.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>