mhi: core: add support to pause or resume data transfer

Some MHI clients needs support to suspend transfers during
device suspend. Adding support to pause or resume pending transfers
without needing to reset the channel state.

CRs-Fixed: 2492779
Change-Id: I961d27d29331f07bf3a08b80ec1133f3b9a59e81
Signed-off-by: Sujeev Dias <sdias@codeaurora.org>