regulator: ab8500: Correct TVOUT regulator enable time

Update TVOUT regulator to match specification.

Was 10ms - changed to 500us.

Signed-off-by: Jonas Aaberg <jonas.aberg@stericsson.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Reviewed-by: Bengt JONSSON <bengt.g.jonsson@stericsson.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>