mhi: add snapshot for MHI driver stack

This change ports MHI driver stack and it's dependencies
from msm-4.14 kernel. All the files are as is from msm-4.14.
Additional changes were made to pass check_patch errors.

This MHI driver stack snapshot is taken as of msm-4.14

'commit: <b5ca255f>
("Merge "regulator: qpnp-lcdb: Correct the get_voltage calculation"")'

CRs-Fixed: 2313588
Change-Id: I17422e80f437eb2aa42a98dd5d451b42e45646db
Signed-off-by: Sujeev Dias <sdias@codeaurora.org>