sata: Add SATA driver with DMA support for Marvell Kirkwood and Armada XP

This patch adds a new SATA driver for the Marvell Kirkwood and Armada
370 / XP SoC's.

This driver supports the SATA controller of some Mavell SoC's.
Here a (most likely incomplete) list of the supported SoC's:
- Kirkwood
- Armada 370
- Armada XP

This driver implementation is an alternative to the already available
driver via the "ide" commands interface (drivers/block/mvsata_ide.c).
But this driver only supports PIO mode and as this new driver also
supports transfer via DMA, its much faster.

Please note, that the newer SoC's (e.g. Armada 38x) are not supported
by this driver. As they have an AHCI compatible SATA controller
integrated.

The original version of this driver was sent by Tor Krill to the U-Boot
list a few years ago. Here the link:

http://lists.denx.de/pipermail/u-boot/2010-June/073147.html



Changes by Stefan:
- Coding-style cleanup
- Support for Armada XP added
- MBUS window setup added
- D-cache flush and invalidation added - works with dcache enabled on
  Armada XP
- Removed mdelay() from ata_wait_register() and add timer based timeout
  detection to speed up the transfer

Signed-off-by: Tor Krill <tor@excito.com>
Signed-off-by: Stefan Roese <sr@denx.de>
Cc: Luka Perkov <luka.perkov@sartura.hr>
Cc: Tom Rini <trini@konsulko.com>