msm: msm_bus: Change the init level for bus scaling driver

Change the driver init level for bus scaling driver to
fs_initcall as it has dependency on clock driver which is
probed at subsys_initcall level.

Change-Id: Iaa32c4c37c2762092c90f551d394d81d5baaca33
Signed-off-by: Odelu Kukatla <okukatla@codeaurora.org>