Add support for AMD's Bolton chipset. The SPI controller on the bolton chipset uses the same 3-bit speed settings as yangtze, but is otherwise the same as the hudson chips. Note that the Bolton RRG doesn't specify a speed setting for the bit setting of 0b111, so I'm assuming that it's the same setting as yangtze.
Signed-off-by: Martin Roth martin.roth@se-eng.com