ASoC: dapm: Make sure we update the bias level for CODECs with no op

Commit 412312 (ASoC: dapm: Make sure all dapm contexts are updated)
ensures that we update non-CODEC DAPM contexts but means that if a
CODEC has no set_bias_level() operation it'll not be updated. Fix
that.

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