usb: typec: tcpm: Support for Alternate Modes

This adds more complete handling of VDMs and registration of
partner alternate modes, and introduces callbacks for
alternate mode operations.

Only DFP role is supported for now.

Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Tested-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>