iio: meter: ina230: power on if current_threshold defined

iio: meter: ina230: power on if current_threshold defined

Power it on after initializatin in case current_threshold
is defined in device tree, or power it down.

Bug 200012361

Change-Id: Ic1b463af1812bf47b01ce04dc7714fb7965629e0
Signed-off-by: Roger Hsieh <rhsieh@nvidia.com>
Reviewed-on: http://git-master/r/434620
Reviewed-by: Timo Alho <talho@nvidia.com>
Reviewed-by: Deepak Nibade <dnibade@nvidia.com>
Reviewed-by: Jinyoung Park <jinyoungp@nvidia.com>
Reviewed-by: Bharat Nihalani <bnihalani@nvidia.com>