ARM: zynq: DT: Remove DMA from board DTs

The DMA engine is enabled for all DTs that derive from zynq-7000.dtsi.
There is no need to override the 'status' property in board DTs.

Signed-off-by: Soren Brinkmann <soren.brinkmann@xilinx.com>
Reviewed-by: Andreas Färber <afaerber@suse.de>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>