ASoC: Use a normal cache sync for WM8903

The driver used to use a complicated method to sync the register cache
after having brought the bias level up to standby in resume due to the
use of the write sequencer to manage the initial power up. Now that we
don't use the write sequencer there is no need for this and we can just
use snd_soc_cache_sync() directly.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Tested-by: Stephen Warren <swarren@nvidia.com>