bus: mhi: core: Add support for creating and destroying MHI devices

This commit adds support for creating and destroying MHI devices. The
MHI devices binds to the MHI channels and are used to transfer data
between MHI host and client device.

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 from pm 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/20200220095854.4804-5-manivannan.sadhasivam@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>