spelling: s/usefull/useful/

Signed-off-by: Adrian Bunk <bunk@stusta.de>
diff --git a/Documentation/power/swsusp.txt b/Documentation/power/swsusp.txt
index cd0fcd8..08c79d4 100644
--- a/Documentation/power/swsusp.txt
+++ b/Documentation/power/swsusp.txt
@@ -212,7 +212,7 @@
 
 cat `cat /proc/[0-9]*/maps | grep / | sed 's:.* /:/:' | sort -u` > /dev/null
 
-after resume. swapoff -a; swapon -a may also be usefull.
+after resume. swapoff -a; swapon -a may also be useful.
 
 Q: What happens to devices during swsusp? They seem to be resumed
 during system suspend?
@@ -323,7 +323,7 @@
 A: No, it should work okay, as long as your app does not mlock()
 it. Just prepare big enough swap partition.
 
-Q: What information is usefull for debugging suspend-to-disk problems?
+Q: What information is useful for debugging suspend-to-disk problems?
 
 A: Well, last messages on the screen are always useful. If something
 is broken, it is usually some kernel driver, therefore trying with as