Add support for transferring data between external modem and host
processor using MHI protocol.
This is based on the patch submitted by Sujeev Dias:
https://lkml.org/lkml/2018/7/9/988
Signed-off-by: Sujeev Dias <sdias@xxxxxxxxxxxxxx>
Signed-off-by: Siddartha Mohanadoss <smohanad@xxxxxxxxxxxxxx>
[mani: splitted the data transfer patch and cleaned up for upstream]
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@xxxxxxxxxx>