arm: imx: add i.MX53 Beckhoff CX9020 Embedded PC

Add CX9020 board based on mx53loco.
Add simplified imx53 base device tree from kernel v4.8-rc8, to reuse
serial_mxc with DTE and prepare for device tree migration of other
functions and imx53 devices.

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

Signed-off-by: Patrick Bruenn <p.bruenn@beckhoff.com>
diff --git a/arch/arm/dts/Makefile b/arch/arm/dts/Makefile
index fde1232..b8e1342 100644
--- a/arch/arm/dts/Makefile
+++ b/arch/arm/dts/Makefile
@@ -293,6 +293,8 @@
 	pcm052.dtb \
 	bk4r1.dtb
 
+dtb-$(CONFIG_MX53) += imx53-cx9020.dtb
+
 dtb-$(CONFIG_MX6) += imx6ull-14x14-evk.dtb \
 	imx6sll-evk.dtb \
 	imx6dl-icore.dtb \