ASoC: wm8962: Clean up error handling for failed FLL start

Don't record the FLL as having started and leave the hardware disabled
ensuring we are in a better state if this does happen to be a transient
error and making debugging easier.

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