msm: msm_bus: Add snapshot of msm_bus driver

Initial port of msm bus codebase into new kernel version from msm-4.4,
commit f600d8b9ec91f ("msm-core: Move get_user out side critical section")

Change-Id: I596f206fc841f46ac08b963093680df26255917c
Signed-off-by: David Dai <daidavid1@codeaurora.org>