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/edac.txt b/Documentation/edac.txt
index 56c7e93..8bdc07c 100644
--- a/Documentation/edac.txt
+++ b/Documentation/edac.txt
@@ -550,7 +550,7 @@
 	/sys/devices/systm/edac/test-instance
 
 in this directory are various controls, a symlink and one or more 'instance'
-directorys.
+directories.
 
 The standard default controls are: