Adds libmctp as a west module dependency

Signed-off-by: Tom Burdick <thomas.burdick@intel.com>

libmctp provides interfaces for wiring up a MCTP bus it calls bus
bindings. The bindings provided in libmctp however are not directly
useful to Zephyr without some work. Provide an initial uart binding that
directly uses Zephyr's async uart interface.

Signed-off-by: Tom Burdick <thomas.burdick@intel.com>

Samples work by sending MCTP encoded messages over a uart between two
boards.

Signed-off-by: Tom Burdick <thomas.burdick@intel.com>

Adds myself, nashif, and inteljiangwe1 to the maintainers file covering
the libmctp module.

Signed-off-by: Tom Burdick <thomas.burdick@intel.com>