[U-Boot] Xilinx Zynq platform

[Michal Simek]

Hi,

I am sending basic support for new Xilinx Zynq platform.
It is new ARM cortex a9 cpu with programmable logic.
For more information look at www.xilinx.com/zynq.

In future we are going to extend this platform for i2c, spi,
mmc, fpga, nand, nor support, and maybe more. 
These drivers will be send in the next round when this series
is applied to mainline.

Also this platform can also use all drivers targetted to 
Microblaze (axi) for example emaclite, axi ethernet, uartlite,
ns16550a, etc. 

As all others Xilinx platforms this is candidate for OF driven 
configuration.

It is tested on ZC702 platform.

Thanks for your review.

Thanks,
Michal