typec: tcpm: Add ADO header for Alert message handling

This commit adds a header providing definitions for handling Alert
messages. Currently the header only focuses on handling incoming
alerts.

Signed-off-by: Adam Thomson <Adam.Thomson.Opensource@diasemi.com>
Acked-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>