mhi_bus: core: Add support for MHI host interface

MHI Host Interface is a communication protocol to be used by the host
to control and communcate with modem over a high speed peripheral bus.
This module will allow host to communicate with external devices that
support MHI protocol.

CRs-Fixed: 2204910
Change-Id: I6057f9167ebbb5d4dc2ebb91e46ede6bc7054325
Signed-off-by: Sujeev Dias <sdias@codeaurora.org>