Perform actual driver registration right in serio_register_driver()
instead of offloading it to kseriod and return proper error code to
callers if driver registration fails.

Note that driver <-> port matching is still done by kseriod to
speed up boot process since probing for PS/2 mice and keyboards
is pretty slow.
Signed-off-by: NDmitry Torokhov <dtor@mail.ru>