Input: altera_ps2 - write to correct register when disabling interrupts

In altera_ps2_close, the data register (offset 0) is written instead of
the control register (offset 4), leading to the RX interrupt not being
disabled. Fix this by calling writel() with the offset for the proper
register.

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