soc: qcom: service-notifier: Use high priority wq for PDR

Use unbound and high priority workqueue for handling
indications from PDs, and sending ACKs, quickly
during PDR.

Change-Id: I617504cf0107b05b635e77fb3e5593d68ed69dbd
Signed-off-by: Isaac J. Manjarres <isaacm@codeaurora.org>