mhi: mhi_rmnet: pass maximum payload size to mhi during registration

MHI host require clients to provide maximum payload size
during active transfer so MHI host can pre-allocate bounce
buffers.

CRs-Fixed: 1110280
Change-Id: I9a8fcb8dbb711cdd35dfc12b47b4381bf0985134
Signed-off-by: Sujeev Dias <sdias@codeaurora.org>