arm: dts: Add zephyr,console to missing device trees

The chosen property that sets which serial port is being used for the
console device wasn't set.  Add the property "zephyr,console" to the
Arduino Due, CC3200-LaunchXL, CC3220SF-LaunchXL, and QEMU Cortex M3
boards.

Signed-off-by: Kumar Gala <kumar.gala@linaro.org>