ASoC: arizona: Correct relationship between VCO corner and Fref

When configuring the FLL we must ensure that the reference clock passed
to the FLL is under a certain limit. This limit was specified
incorrectly in the current code, this patch corrects this. Although the
error will only be encountered in some edge cases.

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