Fix typos in comments and documentation.

libs/libc/semaphore/sem_init.c

@@ -82,7 +82,7 @@ int nxsem_init(FAR sem_t *sem, int pshared, unsigned int value)
 
   if (sem != NULL && value <= SEM_VALUE_MAX)
     {
-      /* Initialize the seamphore count */
+      /* Initialize the semaphore count */
 
       sem->semcount         = (int16_t)value;
 

libs/libc/wqueue/work_queue.c

@@ -61,7 +61,7 @@
  *
  * Description:
  *   Queue work to be performed at a later time.  All queued work will be
- *   performed on the worker thread of of execution (not the caller's).
+ *   performed on the worker thread of execution (not the caller's).
  *
  *   The work structure is allocated by caller, but completely managed by
  *   the work queue logic.  The caller should never modify the contents of
@@ -132,7 +132,7 @@ static int work_qqueue(FAR struct usr_wqueue_s *wqueue,
  *
  * Description:
  *   Queue user-mode work to be performed at a later time.  All queued work
- *   will be performed on the worker thread of of execution (not the caller's).
+ *   will be performed on the worker thread of execution (not the caller's).
  *
  *   The work structure is allocated and must be initialized to all zero by
  *   the caller.  Otherwise, the work structure is completely managed by the