msm: mhi_dev: Add ADB SW channel support in UCI driver

Add a new UCI SW channel for ADB communication over MHI/PCIE. The char
device file node for ADB is created after MHI is in active state.

Change-Id: I249a9935af9cb70b0294061e5df0818c97a5ddba
Signed-off-by: Siva Kumar Akkireddi <sivaa@codeaurora.org>