perf tools: Add util function for overriding user set config values

perf tools: Add util function for overriding user set config values

There is some duplicated code to only override config values if they
haven't already been set by the user so make a util function for this.

Signed-off-by: James Clark <james.clark@arm.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Denis Nikitin <denik@google.com>
Cc: Ian Rogers <irogers@google.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@linaro.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Mike Leach <mike.leach@linaro.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Suzuki Poulouse <suzuki.poulose@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Yang Shi <shy828301@gmail.com>
Cc: coresight@lists.linaro.org
Cc: linux-arm-kernel@lists.infradead.org
Link: https://lore.kernel.org/r/20230424134748.228137-3-james.clark@arm.com
[ Moved evsel__set_config_if_unset() to util/pmu.c to avoid dragging stuff into the python binding ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>