selftests/resctrl: Fix resctrl_tests' return code to work with selftest framework

In kselftest framework, if a sub test can not run by some reasons,
the test result should be marked as SKIP rather than FAIL.
Return KSFT_SKIP(4) instead of KSFT_FAIL(1) if resctrl_tests is not run
as root or it is run on a test environment which does not support resctrl.

 - ksft_exit_fail_msg(): returns KSFT_FAIL(1)
 - ksft_exit_skip(): returns KSFT_SKIP(4)
Reviewed-by: Shuah Khan <skhan@linuxfoundation.org>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Reviewed-by: Fenghua Yu <fenghua.yu@intel.com>
Signed-off-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

tools/testing/selftests/resctrl/resctrl_tests.c

@@ -225,7 +225,7 @@ int main(int argc, char **argv)
 	 * 2. We execute perf commands
 	 */
 	if (geteuid() != 0)
-		return ksft_exit_fail_msg("Not running as root, abort testing.\n");
+		return ksft_exit_skip("Not running as root. Skipping...\n");
 
 	if (has_ben) {
 		/* Extract benchmark command from command line. */
@@ -252,7 +252,7 @@ int main(int argc, char **argv)
 	sprintf(bm_type, "fill_buf");
 
 	if (!check_resctrlfs_support())
-		return ksft_exit_fail_msg("resctrl FS does not exist\n");
+		return ksft_exit_skip("resctrl FS does not exist. Enable X86_CPU_RESCTRL config option.\n");
 
 	filter_dmesg();