Move DMA-mapping.txt to Documentation/PCI/.

DMA-mapping.txt was supposed to be moved from Documentation/ to
Documentation/PCI/.  The 00-INDEX files in those two directories
were updated, along with a few other text files, but the file
itself somehow escaped being moved, so move it and update more
text files and source files with its new location.
Signed-off-by: NRandy Dunlap <randy.dunlap@oracle.com>
Acked-by: NGreg Kroah-Hartman <gregkh@suse.de>
cc:	Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This patch updates some of the documentation about DMA buffer management
for USB, and ways to avoid extra copying.  Our understanding of the issues
has improved over time.

 - Most drivers should *avoid* the dma-coherent allocators.  There are
   a few exceptions (like the HID driver).

 - Some methods are currently commented out; it seems folk writing
   USB drivers aren't doing performance tuning at that level yet.

 - Just avoid highmem; there's no good way to pass an "I can do highmem
   DMA" capability through a driver stack.  This is easy, everything
   already avoids highmem.  But it'd be nice if x86_32 systems with much
   physical memory could use it directly with network adapters and mass
   storage devices.  (Patch, anyone?)
Signed-off-by: NDavid Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!