ARM: dts: socfpga: Fix NAND controller node compatible

The compatible string for the Denali NAND controller is incorrect,
fix it by replacing it with one matching the DT bindings and the
driver.

Cc: stable@vger.kernel.org
Signed-off-by: Marek Vasut <marex@denx.de>
Fixes: d837a80d ("ARM: dts: socfpga: add nand controller nodes")
Cc: Steffen Trumtrar <s.trumtrar@pengutronix.de>
Signed-off-by: Dinh Nguyen <dinguyen@kernel.org>