hikirk u-boot: Add FTD support

Add device tree support.

Signed-off-by: Mario Schuknecht <mario.schuknecht@dresearch-fe.de>
hikirk u-boot: Speed up mmc

Remove udelay, because card status is polled in a loop.

Signed-off-by: Mario Schuknecht <mario.schuknecht@dresearch-fe.de>