mhi: mhi_uci: redesign mhi_uci driver

As a prerequisite for subsystem restart support,
redesign driver main operations such as open,
read, write, poll, and close methods.

CRs-Fixed: 1097560
Change-Id: I7eb99a09de75a2afa1eb408cace6a03dca85f5fe
Signed-off-by: Sujeev Dias <sdias@codeaurora.org>