mhi: core: add support for reserve side coalesced (rsc) channels

RSC channels allow hardware to combine multiple small IP packets
into single jumbo IP packet before transferring to host to reduce
mips consumption.

CRs-Fixed: 2361266
Change-Id: I710233427b6211124af05c0c0a10f2954029e46f
Signed-off-by: Sujeev Dias <sdias@codeaurora.org>