doc: spelling error changes

Fixed multiple spelling errors.

Acked-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Carlos E. Garcia <carlos@cgarcia.org>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
diff --git a/Documentation/s390/monreader.txt b/Documentation/s390/monreader.txt
index beeaa4b..d372958 100644
--- a/Documentation/s390/monreader.txt
+++ b/Documentation/s390/monreader.txt
@@ -10,7 +10,7 @@
 Description
 ===========
 This item delivers a new Linux API in the form of a misc char device that is
-useable from user space and allows read access to the z/VM Monitor Records
+usable from user space and allows read access to the z/VM Monitor Records
 collected by the *MONITOR System Service of z/VM.