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/drivers/usb/host/sl811-hcd.c b/drivers/usb/host/sl811-hcd.c
index 94d859a..ba370c5 100644
--- a/drivers/usb/host/sl811-hcd.c
+++ b/drivers/usb/host/sl811-hcd.c
@@ -1556,7 +1556,7 @@
 		hcd->power_budget = sl811->board->power * 2;
 	}
 
-	/* enable power and interupts */
+	/* enable power and interrupts */
 	port_power(sl811, 1);
 
 	return 0;