msm: msm_bus: remove the buspm file

Remove the empty buspm module from msm_bus since it adds
no functionality to the bus bandwidth aggregation
driver. Also change the dev_info message to dev_dbg
to make sure there are no unnecessary messages.

Change-Id: Ief4abcb5be4178bb86913c5e871b055d6d21ca8c
Signed-off-by: Kiran Gunda <kgunda@codeaurora.org>