libperf tests: Fix typo in perf_evlist__open() failure error messages

libperf tests: Fix typo in perf_evlist__open() failure error messages

This patch corrects typos in error messages. I should be "evlist", not
"evsel" as the function that fails is perf_evlist__open().

Fixes: 5948fd7d6e5ca187 ("libperf: Move to tools/lib/perf")
Fixes: 19330c0fc81669a8 ("libperf tests: Add test_stat_multiplexing test")
Signed-off-by: Shunsuke Nakamura <nakamura.shun@fujitsu.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lore.kernel.org/lkml/20220325043829.224045-2-nakamura.shun@fujitsu.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>