net: ipc_router: Reference count server

Everytime a server is searched and then accessed, a global lock is
used to protect the access for its entire duration.

Define a reference element in the server. Get a reference to the server
everytime it is searched and accessed. Put the reference back once the
access is complete. Release the server when the reference count is zero.

Change-Id: Ice11a6d3ef86c3c49b43d8c7b6c04df260dca28c
Signed-off-by: Karthikeyan Ramasubramanian <kramasub@codeaurora.org>