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/drivers/serial/Kconfig b/drivers/serial/Kconfig
index 620dd82..b26ada3 100644
--- a/drivers/serial/Kconfig
+++ b/drivers/serial/Kconfig
@@ -325,7 +325,7 @@
 
 config MXC_UART
 	bool "IMX serial port support"
-	depends on MX6
+	depends on MX5 || MX6
 	help
 	  If you have a machine based on a Motorola IMX CPU you
 	  can enable its onboard serial port by enabling this option.