mainboard/lenovo/t520: too many arguments to pc_keyboard_init

Fix build regression introduced in:
a823f9b mainboard/lenovo: Add Lenovo Thinkpad T520 support

Change-Id: I60d92f8cceda6427f43e6be9d78c2af82af4b061
Signed-off-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
Reviewed-on: http://review.coreboot.org/5738
Tested-by: build bot (Jenkins)
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>