ide: add at91_ide driver

This is IDE host driver for AT91 (SAM9, CAP9, AT572D940HF) Static Memory
Controller with Compact Flash True IDE Mode logic.

Driver have to switch 8/16 bit bus width when accessing Task Tile or Data
Register. Moreover some extra things need to be done when setting PIO mode.
Only PIO mode is used, hardware have no DMA support. If interrupt line is
connected through GPIO extra quirk is needed to cope with fake interrupts.

Signed-off-by: Stanislaw Gruszka <stf_xl@wp.pl>
Cc: Andrew Victor <avictor.za@gmail.com>
Acked-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>