Documentation: Remove device connection documentation

The API that allowed device connection descriptions to
be added is now removed, so removing also the documentation
for it.

Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Link: https://lore.kernel.org/r/20200907120532.37611-3-heikki.krogerus@linux.intel.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>