net: Add Qualcomm IPC router

Add an implementation of Qualcomm's IPC router protocol, used to
communicate with service providing remote processors.

Signed-off-by: Courtney Cavin <courtney.cavin@sonymobile.com>
Signed-off-by: Bjorn Andersson <bjorn.andersson@sonymobile.com>
[bjorn: Cope with 0 being a valid node id and implement RTM_NEWADDR]
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>