mhi: mhi_uci: add support for shutdown and system error notification

Add support to handle system error and shutdown
notifications from mhi host.

CRs-Fixed: 1097560
Change-Id: Ied6c907586aa4dc2ed3b1a7c19305877144b3b21
Signed-off-by: Sujeev Dias <sdias@codeaurora.org>