msm: msm_bus: initialize the local variable

Initialize the local variable 'ret' which is returned
from the function.

Change-Id: Ie82e74ce55b622db924e353a6ea98323c7642fa6
Signed-off-by: Kiran Gunda <kgunda@codeaurora.org>
Signed-off-by: Odelu Kukatla <okukatla@codeaurora.org>