ASoC: max98090: sync regcache on entering STANDBY

Sync regcache when entering STANDBY from OFF.  ON isn't entered with
OFF as the current state, so the registers were not being re-synced
after suspend/resume.

The 98088 and 98095 already call regcache_sync from STANDBY.

Signed-off-by: Dylan Reid <dgreid@chromium.org>
Signed-off-by: Mark Brown <broonie@linaro.org>
Cc: stable@vger.kernel.org