ASoC: arizona: Support new fratio encoding on the wm5110 rev D

The reference clock path on newer IP FLLs requires a different
configuration, and should avoid integer mode operation. This patch adds
support for both the new encoding and updates the calculation.

Signed-off-by: Charles Keepax <ckeepax@opensource.wolfsonmicro.com>
Signed-off-by: Mark Brown <broonie@linaro.org>