regulator: qcom_pm8008-regulator: avoid transactions after suspend

The I2C bus becomes unusable for transactions after it enters
suspend.  Ensure that such transactions are not attempted after
the qcom_pm8008-regulator devices have entered suspend.

Change-Id: Ib13bc2a4a12a79bfe9c8de51ba2dc1ea23fb39c5
Signed-off-by: David Collins <collinsd@codeaurora.org>