ARM: zynq: DT: Add pinctrl information

Add pinctrl descriptions to the zc702 and zc706 device trees.

Signed-off-by: Soren Brinkmann <soren.brinkmann@xilinx.com>
Tested-by: Andreas Färber <afaerber@suse.de>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>