ASoC: sgtl5000: fix VAG power up timing

When power up, a "pop" is heard on line-in and mic-in.
An analysis of the PCM shows it lasts ~400ms
and looks like a filter response.
VAG power up should be delayed by 400ms as VAG power down is.

Signed-off-by: Jean-Michel Hautbois <jean-michel.hautbois@veo-labs.com>
Signed-off-by: Mark Brown <broonie@kernel.org>