sata: Move drivers into new drivers/ata directory

At present we have the SATA and PATA drivers mixed up in the drivers/block
directory. It is better to split them out into their own place. Use
drivers/ata which is what Linux does.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>