iio: light: veml6030: add set up delay after any power on sequence

iio: light: veml6030: add set up delay after any power on sequence

The veml6030 requires a delay of 4 ms after activating the sensor. That
is done correctly during the hw initialization, but it's missing after
resuming.

Move the delay to the power on function to make sure that it is always
observerd. When at it, use fsleep() instead of usleep_range() as such a
narrow range is not required.

Signed-off-by: Javier Carrasco <javier.carrasco.cruz@gmail.com>
Link: https://patch.msgid.link/20241001-veml6035-v3-1-d789f6ff147c@gmail.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>