ARM: dts: socfpga: Fix NAND controller clock supply

ARM: dts: socfpga: Fix NAND controller clock supply

The Denali NAND x-clock should be supplied by nand_x_clk, not by
nand_clk. Fix this, otherwise the Denali driver gets incorrect
clock frequency information and incorrectly configures the NAND
timing.

Cc: stable@vger.kernel.org
Signed-off-by: Marek Vasut <marex@denx.de>
Fixes: c110432668 ("ARM: dts: socfpga: add nand controller nodes")
Cc: Steffen Trumtrar <s.trumtrar@pengutronix.de>
Signed-off-by: Dinh Nguyen <dinguyen@kernel.org>