msm: msm_bus: Make locking during handoff more monolithic

This fixes a race condition during a client bandwidth request
at late_init time whereby a bus device may have its link severed
and connected to a different list, causing null ptr access when
accessing the original commit list.

Change-Id: I469bdf7afb6483ea14b42c8364458d5a954a4166
Signed-off-by: David Dai <daidavid1@codeaurora.org>