cnss2: Enable platform device to be a wakeup source

Currently platform device is not enabled as a wakeup source, so
notifying the PM core for a wakeup event action will be no-op.
Hence enable it during driver probe.

Change-Id: I396e51e1a411f06eb7f6c07c60919bb6c5716fe5
Signed-off-by: Yue Ma <yuem@codeaurora.org>