x86/intel_rdt: Fix incorrect returned value when creating rdgroup sub-directory in resctrl file system

If no monitoring feature is detected because all monitoring features are
disabled during boot time or there is no monitoring feature in hardware,
creating rdtgroup sub-directory by "mkdir" command reports error:

  mkdir: cannot create directory ‘/sys/fs/resctrl/p1’: No such file or directory

But the sub-directory actually is generated and content is correct:

  cpus  cpus_list  schemata  tasks

The error is because rdtgroup_mkdir_ctrl_mon() returns non zero value after
the sub-directory is created and the returned value is reported as an error
to user.

Clear the returned value to report to user that the sub-directory is
actually created successfully.

Signed-off-by: Wang Hui <[email protected]>
Signed-off-by: Zhang Yanfei <[email protected]>
Signed-off-by: Fenghua Yu <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Ravi V Shankar <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Tony Luck <[email protected]>
Cc: Vikas <[email protected]>
Cc: Xiaochen Shen <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>

Author: Wang Hui

arch/x86/kernel/cpu/intel_rdt_rdtgroup.c

@@ -1804,6 +1804,7 @@ static int rdtgroup_mkdir_ctrl_mon(struct kernfs_node *parent_kn,
 		goto out_common_fail;
 	}
 	closid = ret;
+	ret = 0;
 
 	rdtgrp->closid = closid;
 	list_add(&rdtgrp->rdtgroup_list, &rdt_all_groups);