perf mem: Fix the wrong reference in parse_record_events()

A segmentation fault can be triggered when running
'perf mem record -e ldlat-loads'

The commit 35b38a71c92fa033 ("perf mem: Rework command option handling")
moves the OPT_CALLBACK of event from __cmd_record() to cmd_mem().

When invoking the __cmd_record(), the 'mem' has been referenced (&).

So the &mem passed into the parse_record_events() is a double reference
(&&) of the original struct perf_mem mem.

But in the cmd_mem(), the &mem is the single reference (&) of the
original struct perf_mem mem.

Fixes: 35b38a71c92fa033 ("perf mem: Rework command option handling")
Signed-off-by: Kan Liang <[e-mail]>
Cc: Adrian Hunter <[e-mail]>
Cc: Ian Rogers <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/builtin-mem.c

···
 static int parse_record_events(const struct option *opt,
 			       const char *str, int unset __maybe_unused)
 {
-	struct perf_mem *mem = *(struct perf_mem **)opt->value;
+	struct perf_mem *mem = (struct perf_mem *)opt->value;
 	struct perf_pmu *pmu;
 
 	pmu = perf_mem_events_find_pmu();