ARM: dts: imx6ul: Add Variscite Concerto board support

ARM: dts: imx6ul: Add Variscite Concerto board support

Add support for the Variscite Concerto Carrier Board with:

- LVDS interface for the VLCD-CAP-GLD-LVDS 7" LCD 800 x 480 touch
  display (not configured)
- USB Host + USB OTG Connector
- 10/100 Mbps Ethernet
- miniPCI-Express slot
- SD Card connector
- Audio Headphone/Line In jack connectors
- S-ATA
- On-board DMIC

Product Page: https://www.variscite.com/product/single-board-computers/concerto-board

This file is based on the one provided by Variscite on their own kernel,
but adapted for mainline.

Signed-off-by: Antonin Godard <antonin.godard@bootlin.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>