net: ipc_router: Use kthread to read data

Improve the RX latencies by moving reader work from global kwroker to
separate kworker thread and increase RT priority to support high speed
sensor sampling use case.

CRs-Fixed: 2261724
Change-Id: I74bb7867e2f349b982823e73d07332a71614810f
Signed-off-by: Arun Kumar Neelakantam <aneela@codeaurora.org>