ASoC: arizona: Don't change the FLLn_GAIN before entering FREERUN

When reclocking an active FLL, to ensure a clean transition, do
not change the gain setting until we have entered free run.

Signed-off-by: Nariman Poushin <nariman@opensource.wolfsonmicro.com>
Signed-off-by: Charles Keepax <ckeepax@opensource.wolfsonmicro.com>
Signed-off-by: Mark Brown <broonie@kernel.org>