arm64: dts: imx8mm: Enable CPLD_Dn pull down resistor on MX8Menlo

Enable CPLD_Dn pull down resistor instead of pull up to avoid
intefering with CPLD power off functionality.

Fixes: 510c527b ("arm64: dts: imx8mm: Add i.MX8M Mini Toradex Verdin based Menlo board")
Signed-off-by: Marek Vasut <marex@denx.de>
Reviewed-by: Fabio Estevam <festevam@denx.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>