Documentation: remove duplicated words

Remove many duplicated words under Documentation/ and do other small
cleanups.

Examples:
        "and and" --> "and"
        "in in" --> "in"
        "the the" --> "the"
        "the the" --> "to the"
        ...

Signed-off-by: Paolo Ornati <ornati@fastwebnet.it>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
diff --git a/Documentation/rpc-cache.txt b/Documentation/rpc-cache.txt
index 21fb09c..8a382be 100644
--- a/Documentation/rpc-cache.txt
+++ b/Documentation/rpc-cache.txt
@@ -53,7 +53,7 @@
 		structure
 	void cache_put(struct kref *)
 		This is called when the last reference to an item is
-		is dropped.  The pointer passed is to the 'ref' field
+		dropped.  The pointer passed is to the 'ref' field
 		in the cache_head.  cache_put should release any
 		references create by 'cache_init' and, if CACHE_VALID
 		is set, any references created by cache_update.