uboot-imx

arm: zynq: Rework FPGA initialization

This commit moves the FPGA descriptor definition
to mach-zynq, where it makes more sense.

Based on patches from Ariel D'Alessandro <ariel@vanguardiasur.com.ar>
and Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>

Signed-off-by: Michal Simek <michal.simek@xilinx.com>