zynq: Add Zynq PicoZed board support

The PicoZed is a System-on-Module board which is marketed as part of
the ZedBoard/MicroZed/etc. collection. It includes a Zynq-7000
processor.

This patch adds support that covers all the variants of the PicoZed
including the SKUs with Z7010/Z7020 and Z7015/Z7030 Zynq chips. This
patch set however only covers support for the System-on-Module and does
not cover any extra components that are available on carrier boards
(except those that are fanned out of the module itself).

More information on this board, its variants and available carrier
boards is available at: http://zedboard.org/product/picozed



Signed-off-by: Nathan Rossi <nathan.rossi@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>