ARM: dts: imx: add CX9020 Embedded PC device tree

The CX9020 differs from i.MX53 Quick Start Board by:
- use uart2 instead of uart1
- DVI-D connector instead of VGA
- no audio
- no SATA connector
- CCAT FPGA connected to emi
- enable rtc

Signed-off-by: Patrick Bruenn <p.bruenn@beckhoff.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>