ARM: zynq: defconfig: Enable CMA support

Enable CMA support and set limit to 128MB.
Xilinx DRM  driver uses CMA for allocating
contiguous memory blocks.

Signed-off-by: Radhey Shyam Pandey <radheys@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>