Input: iforce - move get_id to the transport operations

To avoid #ifdef-ing out parts of the code and having conditionals in normal
control flow, let's define "get_id" transport method and move
implementation into respective transport modules.

Tested-by: Tim Schumacher <timschumi@gmx.de>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>