ARM: dts: socfpga: add pl330 clock

The pl330 dmac won't be added to the list of amba devices, as it doesn't have
a clock entry.
Add the clock.

Signed-off-by: Steffen Trumtrar <s.trumtrar@pengutronix.de>
Signed-off-by: Dinh Nguyen <dinguyen@altera.com>