msm: msm_bus: Do not disconnect ports during init

Due to the fact that we can't guarantee probe ordering of
the bus proxy client before any other consumers, there may
be cases where bus disconnects happen prematurely before a
consumer has had a chance to probe. Eliminate that possibility
by only allowing bus disconnects post late_init.

Change-Id: I86b05401c68bbbb24967385819a673e9b9a46eb9
Signed-off-by: David Dai <daidavid1@codeaurora.org>