ASoC: arizona: Don't enable FLL on REFCLK configuration

Enabling the FLL when REFCLK is being configured is not what the user
would expect and can cause issues if SYNCCLK has no specified frequency.

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