Grabbed zynq specific files from Xilinx's u-boot fork, commit b904725.

Modified some common i.MX6 files with Xilinx u-boot specific changes.

https://github.com/Xilinx/u-boot-xlnx/tree/b904725a112f7b7a1b5d657541d77dc8fa1a1615

Change-Id: Ib90372873f7e2dc8d2a268735326ef9d97468bc0

Grabbed common files from Data61's i.MX6 driver.

Since the driver structure between the i.MX6 and the Zynq7000
is very similar, it would be nice to have a new directory for
source files that is arch/arm. However, all the files in the
u-boot directory reference headers locally, and including these
files in the plat_include or arch_include directory makes it
nearly impossible to reference local files. This is something
to do at a later time.

Change-Id: Ic37753496680a6975f2ea6f25bb5049459b14183