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>

kernel/hrtimer.c

@@ -412,7 +412,7 @@ static int hrtimer_reprogram(struct hrtimer *timer,
 	/*
 	 * When the callback is running, we do not reprogram the clock event
 	 * device. The timer callback is either running on a different CPU or
-	 * the callback is executed in the hrtimer_interupt context. The
+	 * the callback is executed in the hrtimer_interrupt context. The
 	 * reprogramming is handled either by the softirq, which called the
 	 * callback or at the end of the hrtimer_interrupt.
 	 */