rtla/utils: Use calloc and check the potential memory allocation failure

Replace malloc with calloc and add memory allocating check
of mon_cpus before used.

Link: https://lkml.kernel.org/r/20220615073348.6891-1-jianchunfu@cmss.chinamobile.com

Fixes: 7d0dc95 ("rtla/timerlat: Add --dma-latency option")
Signed-off-by: jianchunfu <jianchunfu@cmss.chinamobile.com>
Acked-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

tools/tracing/rtla/src/utils.c

@@ -106,8 +106,9 @@ int parse_cpu_list(char *cpu_list, char **monitored_cpus)
 
 	nr_cpus = sysconf(_SC_NPROCESSORS_CONF);
 
-	mon_cpus = malloc(nr_cpus * sizeof(char));
-	memset(mon_cpus, 0, (nr_cpus * sizeof(char)));
+	mon_cpus = calloc(nr_cpus, sizeof(char));
+	if (!mon_cpus)
+		goto err;
 
 	for (p = cpu_list; *p; ) {
 		cpu = atoi(p);