bus: mhi: core: Add support for downloading RDDM image during panic

MHI protocol supports downloading RDDM (RAM Dump) image from the
device through BHIE. This is useful to debugging as the RDDM image
can capture the firmware state.

This is based on the patch submitted by Sujeev Dias:
https://lkml.org/lkml/2018/7/9/989



Signed-off-by: Sujeev Dias <sdias@codeaurora.org>
Signed-off-by: Siddartha Mohanadoss <smohanad@codeaurora.org>
[mani: splitted the data transfer patch and cleaned up for upstream]
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Reviewed-by: Jeffrey Hugo <jhugo@codeaurora.org>
Tested-by: Jeffrey Hugo <jhugo@codeaurora.org>
Link: https://lore.kernel.org/r/20200220095854.4804-10-manivannan.sadhasivam@linaro.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>