msm: ipc: Load default subsystem under appropriate scenario

Only client and service ports are used for communication with the remote
subsystems. Load the default subsystem only when the clients lookup their
services or when the local services get registered with the IPC Router.

Change-Id: I18729bb849c656a826de4f67f9ffe159dd3cf5f6
Signed-off-by: Karthikeyan Ramasubramanian <kramasub@codeaurora.org>