Input: altera_ps2 - switch to using managed resources

Use them devm_ managed resources API to simplify error handling in
altera_ps2_probe() and to reduce the size of altera_ps2_remove() and the
ps2if struct.

Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>