Fix common misspellings

Fixes generated by 'codespell' and manually reviewed.

Signed-off-by: Lucas De Marchi <lucas.demarchi@profusion.mobi>

ipc/msg.c

@@ -704,7 +704,7 @@ long do_msgsnd(int msqid, long mtype, void __user *mtext,
 	msq->q_stime = get_seconds();
 
 	if (!pipelined_send(msq, msg)) {
-		/* noone is waiting for this message, enqueue it */
+		/* no one is waiting for this message, enqueue it */
 		list_add_tail(&msg->m_list, &msq->q_messages);
 		msq->q_cbytes += msgsz;
 		msq->q_qnum++;
@@ -842,7 +842,7 @@ long do_msgrcv(int msqid, long *pmtype, void __user *mtext,
 		 * Disable preemption.  We don't hold a reference to the queue
 		 * and getting a reference would defeat the idea of a lockless
 		 * operation, thus the code relies on rcu to guarantee the
-		 * existance of msq:
+		 * existence of msq:
 		 * Prior to destruction, expunge_all(-EIRDM) changes r_msg.
 		 * Thus if r_msg is -EAGAIN, then the queue not yet destroyed.
 		 * rcu_read_lock() prevents preemption between reading r_msg

ipc/sem.c

@@ -1362,7 +1362,7 @@ SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops,
 	 * semid identifiers are not unique - find_alloc_undo may have
 	 * allocated an undo structure, it was invalidated by an RMID
 	 * and now a new array with received the same id. Check and fail.
-	 * This case can be detected checking un->semid. The existance of
+	 * This case can be detected checking un->semid. The existence of
 	 * "un" itself is guaranteed by rcu.
 	 */
 	error = -EIDRM;

ipc/shm.c

@@ -1056,7 +1056,7 @@ SYSCALL_DEFINE1(shmdt, char __user *, shmaddr)
 	/*
 	 * We need look no further than the maximum address a fragment
 	 * could possibly have landed at. Also cast things to loff_t to
-	 * prevent overflows and make comparisions vs. equal-width types.
+	 * prevent overflows and make comparisons vs. equal-width types.
 	 */
 	size = PAGE_ALIGN(size);
 	while (vma && (loff_t)(vma->vm_end - addr) <= size) {