soc: qcom: stats: Mark device as having no PM support

This driver purely exposes information from memory to the kernel. Let's
mark it as not having any device PM functionality, so that during
suspend we skip even trying to call a suspend function on this device.
This clears up suspend logs more than anything else, but it also shaves
a few cycles off suspend.

Cc: Konrad Dybcio <konrad.dybcio@somainline.org>
Signed-off-by: Stephen Boyd <swboyd@chromium.org>