selftests/cgroup: Fix compile error in test_cpu.c

When compiling the cgroup selftests with the following command:

make -C tools/testing/selftests/cgroup/

the compiler complains as below:

test_cpu.c: In function ‘test_cpucg_nice’:
test_cpu.c:284:39: error: incompatible type for argument 2 of ‘hog_cpus_timed’
  284 |                 hog_cpus_timed(cpucg, param);
      |                                       ^~~~~
      |                                       |
      |                                       struct cpu_hog_func_param
test_cpu.c:132:53: note: expected ‘void *’ but argument is of type ‘struct cpu_hog_func_param’
  132 | static int hog_cpus_timed(const char *cgroup, void *arg)
      |                                               ~~~~~~^~~

Fix it by passing the address of param to hog_cpus_timed().

Fixes: 2e82c0d ("cgroup/rstat: Selftests for niced CPU statistics")
Signed-off-by: Xiu Jianfeng <xiujianfeng@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

Author: Xiu Jianfeng

tools/testing/selftests/cgroup/test_cpu.c

@@ -281,7 +281,7 @@ static int test_cpucg_nice(const char *root)
 
 		/* Try to keep niced CPU usage as constrained to hog_cpu as possible */
 		nice(1);
-		hog_cpus_timed(cpucg, param);
+		hog_cpus_timed(cpucg, &param);
 		exit(0);
 	} else {
 		waitpid(pid, &status, 0);