Add nitrogen6x_qt5_defconfig for to match Qt for Device Creation

The Qt for Device Creation package has some specific configuration
needs to support ADB. Add a configuration that reflects those
changes.

Note that this configuration also includes support for the BRCM
WiFi/BT module used with Nitrogen6_Lite.

More details are available from The Qt Company:
	http://www.qt.io/qt-for-device-creation/

Signed-off-by: Eric Nelson <eric.nelson@boundarydevices.com>