exit/kthread: Fix the kerneldoc comment for kthread_complete_and_exit

I misspelled kthread_complete_and_exit in the kernel doc comment fix
it.

Link: https://lkml.kernel.org/r/202112141329.KBkyJ5ql-lkp@intel.com
Link: https://lkml.kernel.org/r/202112141422.Cykr6YUS-lkp@intel.comReported-by: Nkernel test robot <lkp@intel.com>
Fixes: cead1855 ("exit: Rename complete_and_exit to kthread_complete_and_exit")
Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>

kernel/kthread.c

@@ -294,7 +294,7 @@ void __noreturn kthread_exit(long result)
 }
 
 /**
- * kthread_complete_and exit - Exit the current kthread.
+ * kthread_complete_and_exit - Exit the current kthread.
  * @comp: Completion to complete
  * @code: The integer value to return to kthread_stop().
  *