[coreboot] SeaBIOS and ATA spinup

[Kevin O'Connor]

Hi,

Latest SeaBIOS git should now handle the case where SeaBIOS can't find
drives because it runs before the drives are ready.

The code tries to wait for not-BSY.  However, if the ide bus appears
to be "floating", then it will stop waiting.

Myles - I know you were working around this on your board.  Can you
test if the code in git works for you?

Thanks,
-Kevin