ARM: zynq: Enable DFU functionality in zynq

Enable DFU functionality in zynq.
This DFU functionality helps us to load linux
images on to DDR and can boot linux using bootm.
In order to load images the user should run dfu
command "dfu 0 ram 0" from u-boot prompt and then
send the images from host.

The malloc size has been increased to match the DFU
buffer requirements.

Signed-off-by: Siva Durga Prasad Paladugu <sivadur@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>