ASoC: arizona: Avoid changing SYNC_ENA whilst the FLL_ENA is set

For best performance changing the synchroniser state whilst the FLL is
running should be avoided. As this has been done fairly regularly in
practice rather than hard preventing this, simply improve the FLL enable
sequence and give a warning if the user changes the synchroniser state.

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