Add support for new AMD SPI controller.

This patch adds support for the SPI controllers in Hudson version 3 FCHs
(as found in Kabini and Temash).
BTW it also rewrites sb600spi.c completely.

Tested on ASRock IMB-A180.

Signed-off-by: Wei Hu <wei@aristanetworks.com>
Signed-off-by: Carl-Daniel Hailfinger <c-d.hailfinger.devel.2006@gmx.net>
Signed-off-by: Stefan Tauner <stefan.tauner@student.tuwien.ac.at>