The dev field needs to be set when serio_register_port() is called,
because the open callback may use it (in the error handling path).

Fixes: commit af518342 ("Input: olpc_apsp - check FIFO status on open(), not probe()")
Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>