ipc/util.c: further variable name cleanups

The varable names got a mess, thus standardize them again:

id: user space id. Called semid, shmid, msgid if the type is known.
    Most functions use "id" already.
idx: "index" for the idr lookup
    Right now, some functions use lid, ipc_addid() already uses idx as
    the variable name.
seq: sequence number, to avoid quick collisions of the user space id
key: user space key, used for the rhash tree

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Manfred Spraul <[email protected]>
Cc: Dmitry Vyukov <[email protected]>
Cc: Davidlohr Bueso <[email protected]>
Cc: Davidlohr Bueso <[email protected]>
Cc: Herbert Xu <[email protected]>
Cc: Kees Cook <[email protected]>
Cc: Michael Kerrisk <[email protected]>
Cc: Michal Hocko <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
diff --git a/ipc/sem.c b/ipc/sem.c
index e4df102..26f8e37 100644
--- a/ipc/sem.c
+++ b/ipc/sem.c
@@ -1294,7 +1294,7 @@ static int semctl_info(struct ipc_namespace *ns, int semid,
 			 int cmd, void __user *p)
 {
 	struct seminfo seminfo;
-	int max_id;
+	int max_idx;
 	int err;
 
 	err = security_sem_semctl(NULL, cmd);
@@ -1318,11 +1318,11 @@ static int semctl_info(struct ipc_namespace *ns, int semid,
 		seminfo.semusz = SEMUSZ;
 		seminfo.semaem = SEMAEM;
 	}
-	max_id = ipc_get_maxid(&sem_ids(ns));
+	max_idx = ipc_get_maxidx(&sem_ids(ns));
 	up_read(&sem_ids(ns).rwsem);
 	if (copy_to_user(p, &seminfo, sizeof(struct seminfo)))
 		return -EFAULT;
-	return (max_id < 0) ? 0 : max_id;
+	return (max_idx < 0) ? 0 : max_idx;
 }
 
 static int semctl_setval(struct ipc_namespace *ns, int semid, int semnum,