firmware: xilinx: Add pinctrl support

Adding pinctrl support to query platform specific information (pins)
from firmware.

Signed-off-by: Sai Krishna Potthuri <lakshmi.sai.krishna.potthuri@xilinx.com>
Acked-by: Michal Simek <michal.simek@xilinx.com>
Link: https://lore.kernel.org/r/1619080202-31924-2-git-send-email-lakshmi.sai.krishna.potthuri@xilinx.com


Signed-off-by: Linus Walleij <linus.walleij@linaro.org>