controller: Add connection callbacks

Currently, the connection between the host and a module
can only be created after the module has been detected or
during the interface create. For some controller, we don't
have the choice because they only have a stream that need
to open before any other operation.
But some controller (e.g. TPC/IP) can use more than one stream.
Add connection_create() and connection_destroy() callbacks to
let that kind of controller create more than one connection.

Signed-off-by: Alexandre Bailon <abailon@baylibre.com>