AC97 uses a fixed rate, unrelated to the sample rate. Add a function to
make the setup more trivial.
Signed-off-by: NLucas Stach <dev@lynxeye.de>
Acked-by: NStephen Warren <swarren@nvidia.com>
Signed-off-by: NMark Brown <broonie@opensource.wolfsonmicro.com>