doc: fix some typos

Fix some typos in three documentations.

Signed-off-by: Xishi Qiu <qiuxishi@huawei.com>
Acked-by: Rob Landley <rob@landley.net>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
diff --git a/Documentation/io-mapping.txt b/Documentation/io-mapping.txt
index 473e43b..5ca7842 100644
--- a/Documentation/io-mapping.txt
+++ b/Documentation/io-mapping.txt
@@ -38,7 +38,7 @@
 
 	void io_mapping_unmap_atomic(void *vaddr)
 
-		'vaddr' must be the the value returned by the last
+		'vaddr' must be the value returned by the last
 		io_mapping_map_atomic_wc call. This unmaps the specified
 		page and allows the task to sleep once again.