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>

arch/parisc/kernel/pci-dma.c

@@ -2,7 +2,7 @@
 ** PARISC 1.1 Dynamic DMA mapping support.
 ** This implementation is for PA-RISC platforms that do not support
 ** I/O TLBs (aka DMA address translation hardware).
-** See Documentation/PCI/PCI-DMA-mapping.txt for interface definitions.
+** See Documentation/DMA-API-HOWTO.txt for interface definitions.
 **
 **      (c) Copyright 1999,2000 Hewlett-Packard Company
 **      (c) Copyright 2000 Grant Grundler