clocksource: kona: adapt to CLOCKSOURCE_OF_DECLARE change

The CLOCKSOURCE_OF_DECLARE functions now take a device_node pointer
as their argument, as of the clksrc/cleanup branch in arm-soc.
This patch adapts the bcm_kona_timer driver to the new interface.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Christian Daudt <csd@broadcom.com>
Cc: John Stultz <john.stultz@linaro.org>