msm: msm_bus: add support for device driver to register with msm bus

Not all msm bus clients are platform devices, adding support
for any device driver to register with msm bus framework.

CRs-Fixed: 2253996
Change-Id: I6c2d65707c11834638084972259bc39d809891a3
Signed-off-by: Sujeev Dias <sdias@codeaurora.org>