net: qrtr: Inform open sockets about new controller

As the higher level communication only deals with "services" the
a service directory is required to keep track of local and remote
services. In order for qrtr clients to be informed about when the
service directory implementation is available some event needs to be
passed to them.

Rather than introducing support for broadcasting such a message in-band
to all open local sockets we flag each socket with ENETRESET, as there
are no other expected operations that would benefit from having support
from locally broadcasting messages.

Cc: Courtney Cavin <ccavin@gmail.com>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>