Fix misspellings of "system", "controller", "interrupt" and "necessary".

Fix the various misspellings of "system", controller", "interrupt" and
"[un]necessary".

Signed-off-by: Robert P. J. Day <rpjday@mindspring.com>
Signed-off-by: Adrian Bunk <bunk@kernel.org>
diff --git a/kernel/sched.c b/kernel/sched.c
index afe76ec..a54bd9d 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -5146,7 +5146,7 @@
 }
 
 /*
- * Figure out where task on dead CPU should go, use force if neccessary.
+ * Figure out where task on dead CPU should go, use force if necessary.
  * NOTE: interrupts should be disabled by the caller
  */
 static void move_task_off_dead_cpu(int dead_cpu, struct task_struct *p)
@@ -5525,7 +5525,7 @@
 
 	case CPU_ONLINE:
 	case CPU_ONLINE_FROZEN:
-		/* Strictly unneccessary, as first user will wake it. */
+		/* Strictly unnecessary, as first user will wake it. */
 		wake_up_process(cpu_rq(cpu)->migration_thread);
 		break;