perf parse-events: Fix legacy cache events if event is duplicated in a PMU

perf parse-events: Fix legacy cache events if event is duplicated in a PMU

The term list when adding an event to a PMU is expected to have the
event name for the alias lookup. Also, set found_supported so that
-EINVAL isn't returned.

Fixes: 62593394f66a ("perf parse-events: Legacy cache names on all
PMUs and lower priority")

Tested-by: Thomas Richter <tmricht@linux.ibm.com>
Signed-off-by: Ian Rogers <irogers@google.com>
Tested-by: James Clark <james.clark@linaro.org>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>