doc: fix broken references

There are numerous broken references to Documentation files (in other
Documentation files, in comments, etc.). These broken references are
caused by typo's in the references, and by renames or removals of the
Documentation files. Some broken references are simply odd.

Fix these broken references, sometimes by dropping the irrelevant text
they were part of.

Signed-off-by: Paul Bolle <pebolle@tiscali.nl>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
diff --git a/include/linux/io-mapping.h b/include/linux/io-mapping.h
index 8cdcc2a1..c81ed2a 100644
--- a/include/linux/io-mapping.h
+++ b/include/linux/io-mapping.h
@@ -27,7 +27,7 @@
  * The io_mapping mechanism provides an abstraction for mapping
  * individual pages from an io device to the CPU in an efficient fashion.
  *
- * See Documentation/io_mapping.txt
+ * See Documentation/io-mapping.txt
  */
 
 #ifdef CONFIG_HAVE_ATOMIC_IOMAP