soc: qcom: pil: use dev_groups and not dev_attrs for bus_type

The dev_attrs field has long been "depreciated" and is finally being
removed, so move the driver to use the "correct" dev_groups field
instead for struct bus_type.

Change-Id: I214e0120af914e7d2d63acac2c421ae405510224
Signed-off-by: Runmin Wang <runminw@codeaurora.org>