msm: msm_bus: skip visited endpoint nodes

Do not exit on path finding if we re-visit a node that is an endpoint,
since multiple paths to the same endpoint can't create a circular path.
The assumption here is that the path with the lowest depth is the correct
one.

Change-Id: Ieafd5bfbe45240672b85024004dc7e33bc62e7d9
Signed-off-by: David Dai <daidavid1@codeaurora.org>