In the SIMtrace and QMOD schematics the LEDs are connected to +3.3V.
Thus to switch the LED on we need to set the pin low.
Change-Id: Id8cc27e6f0b6556ba5e7ea4d254dd0fe59042a0c
This way we can easily check with 'diff' for differences in our code and
Atmel softpack. Also, this layout is more suitable for building various
different firmware images (e.g. factory-test, dfu-loader, main
application) for a variety of different boards (simtrace, owhw, qmod).
