doc: Fix typo in doucmentations

Correct typo (double words) in documentations.

Signed-off-by: Masanari Iida <standby24x7@gmail.com>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

Documentation/rapidio/rapidio.txt

@@ -300,7 +300,7 @@ initialization.
 -------------------------------------------
 
 RapidIO subsystem code organization allows addition of new enumeration/discovery
-methods as new configuration options without significant impact to to the core
+methods as new configuration options without significant impact to the core
 RapidIO code.
 
 A new enumeration/discovery method has to be attached to one or more mport