greybus: connection: unconditionally enable connections

Remove conditional enabling of connections when binding protocols that
served no purpose as a connection either has no bundle or it has an
interface with a valid device id.

Also remove the now unused GB_PROTOCOL_NO_BUNDLE protocol flag.

This is an intermediate step in moving the protocol binding to
connection_init, but is also needed as the control bundle is going away.

Signed-off-by: Johan Hovold <johan@hovoldconsulting.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>