arm64: zynqmp: Disable DP on kd240

When SOM dt is combined with kd240 overlay DPSUB is enabled but kd240 has
no DP wired that's why change disable it via status property.

Signed-off-by: Michal Simek <michal.simek@amd.com>
Link: https://lore.kernel.org/r/f6de217b3350c9d59032ef54800882e48f240398.1706791116.git.michal.simek@amd.com