msm: mhi_dev: Update uevents for MHI UCI channels

Expose both the MHI channel pairs for the current
state whether its connected, disconnected. It allows
clients to be aware of the individual channel states
so it can issue an open once both the channels are
available.

Change-Id: I752b23ba6ea516a78c25ee0f6b125a41788a5885
Signed-off-by: Siddartha Mohanadoss <smohanad@codeaurora.org>