ARM: socfpga: dts: add reset-controller

Add the necessary #reset-cells property to the rst-mgr node and
provide a header-file with all possible resets specified.

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