ASoC: wm8994: Ensure we get a notification on startup for jackdet

Since jackdet only reports deltas it won't generate an interrupt on startup
when a jack is not present. This doesn't make a difference to userspace
but does mean we don't generate a notification via the internal notifier
chains. Fix that by scheduling a work to poll the chip after the clock is
enabled. Use an extremely large timeout since there's no urgency and we
don't want to report a false negative.

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