net: ipc_router: Fix socket reference in IPC Router

The socket associated with an IPC Router port can be released before
the port is released. This leads to an use after free bug in cases
where the socket is closed while a packet is in flight.

Fix the use after free scenario by holding a sock reference during
creation of the port and releasing that in release port function.

CRs-Fixed: 811335
Change-Id: I638cc59e3b4e2347107e5ac19f233b0f7b9dd7b0
Signed-off-by: Atish Kumar Patra <apatra@codeaurora.org>